Heterogeneous Ice Nucleation: The Ultimate Challenge for Molecular Modelling?
September 18, 2018 - September 21, 2018 CECAM-HQ-EPFL, Lausanne, Switzerland
Gabriele C. Sosso The University of Warwick, United Kingdom
Angelos Michaelides University College London, United Kingdom
Tianshu Li George Washington University, USA
1 Description
The formation of ice has an impact across global phenomena such as climate change [1] (ice is a key component of the clouds in our atmosphere) as well as on the microscopic details of water freezing within our own cells [2] (which is of the greatest relevance for cryopreservation). Invariably, though, ice forms heterogeneously, thanks to the presence of impurities boosting the otherwise too low ice nucleation rate of pure water [1,2]. In the last few years we have achieved a good understanding of which substances can promote heterogeneous ice nucleation (HIN): however, we still lack the microscopic insight that would allow us to understand (and predict!) the ice nucleating ability of a given substrate. This is because experiments still struggle to characterize crystal nucleation, which happens on exceedingly small/short length/time scales (ns/nm) [3]. Conversely, molecular simulations, which could indeed provide invaluable insight, are hampered by the fact that [3]:
Accurate interatomic potentials/force fields describing water-water and water-substrate interactions at the same time are needed in order to perform reliable simulations of HIN, typically via classical molecular dynamics. Building such force fields has proven to be an incredibly challenging task. Nucleation is a rare event, as seconds, or days or even weeks are typically needed for a crystalline nucleus to reach its critical size and proceed toward crystallization. Thus, enhanced sampling techniques are almost always needed to tackle the time scale problem via molecular. We are very far away from being able to compare the results of simulations and experiments. For instance, one of the very few quantities that could in principle link the two is the nucleation rate, but a quantitative agreement still eludes us.
The aim of the workshop is to address these issues by devising practical strategies to further the scope, the reliability and the impact of molecular simulations of HIN, in order to bring the latter a step closer to experiments. We build upon the CECAM Workshop "From Atoms to Clouds", held in 2014 in Zurich. This was a success, as it prompted a number of scientific collaborations - one of which led to a paper published in Science [4]. However, within three years from that Workshop we have witnessed amazing advancements in the field of HIN: new enhanced sampling techniques have emerged [5], experiments can now image ice nucleation sites [4], and the first attempts to characterize HIN on biological matter have been reported [6]. Hence the title of this Workshop, " Heterogeneous Ice Nucleation: The Ultimate Challenge for Molecular Modelling?": in contrast with the 2014 Workshop, we will address the practical challenges that simulations will have to overcome in the years to come, and in doing so we will by no means restrict the discussion to atmospheric science. In fact, we have selected as Invited Speakers a blend of the best people with expertise in modelling and experiments of HIN alike: we are thus confident this Workshop will be pivotal in order to take molecular simulations of HIN to the next level.
What's on?
Taking stock: - What do we know about supercooled water that could help us understand the subtleties of Heterogeneous Ice Nucleation (HIN)? - Water on mineral and biological surfaces: how can simulations deal with this level of complexity? Are coarse grained models the solution? - What is it that is preventing the computational community to investigate the formation of ice on biological matter? -- Opportunities: To put together a critical assessment of the computational work that has been done in the field of HIN, in order to build upon this expertise and identifying the most pressing questions to be answered in the near and far future alike.
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Force fields: - Simulations of HIN are delicate: the impact of the computational setup, the flexibility of the substrate... - The future of Force Fields: Whether we need better water/interfaces models in the context of heterogeneous ice nucleation - and how could we proceed to construct them. -- Opportunities: To develop improved water/surface models, with the guidance of experiments and taking advantage of novel approaches such as machine learning-based algorithms.
Simulation Methods & Enhanced Sampling (ES): - Free energy-based ES methods versus path sampling ES methods: pros and cons. - Seeded molecular dynamics: hugely successful for homogenous nucleation - can we extend this framework to HIN? - Software Medley: How to further software development throughout e.g. collaborative coding. -- Opportunities: To devise and implement novel enhanced sampling techniques capable of making molecular simulations HIN more accurate and computationally affordable.
Clathrate Hydrates: - There has been incredibly scarce study on heterogeneous hydrate nucleation: the role of surface in enhancing is much more elusive and controversial, and so it is the role of inhibitors. -- Opportunities: To engage the computational community toward impact of practical relevance for the oil and gas industries, as the formation of hydrates is usually costly (pipelines block) and dangerous.
Bridging the Gap: - Getting Closer to Experiments (Open Discussion D): How to maximize the impact of simulations with respect to experiments and applications - What do atmospheric scientists and cryobiologists need from simulations of HIN? - What are the quantitative and qualitative results that simulations can hope to compare with experimental results? -- Opportunities: (i.) To harness experimental insight (e.g. surface topography) in order to improve simulations and (ii.) To focus experimental work on specific (more accessible computationally) systems.
Future challenges: - From flat, pristine inorganic crystalline (and biological!) surfaces to the actual topographies encountered experimentally (defects, different ice nucleating sites): how do we bridge the gap? - What are the cutting-edge experimental techniques which can hope to achieve the spatial and temporal resolutions characteristic of HIN? - Pinpointing the Challenges: The most pressing challenges for simulations of HIN to be tackled. -- Opportunities: Getting a group of relevant people together could lead to joint European projects/proposals
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Key References
[1] Murray, B.J., O’Sullivan, D., Atkinson, J.D., and Webb, M.E. (2012). Ice nucleation by particles immersed in supercooled cloud droplets. Chem. Soc. Rev. 41, 6519–6554.
[2] John Morris, G., and Acton, E. (2013). Controlled ice nucleation in cryopreservation – A review. Cryobiology 66, 85–92.
[3] Sosso, G.C., Chen, J., Cox, S.J., Fitzner, M., Pedevilla, P., Zen, A., and Michaelides, A. (2016). Crystal Nucleation in Liquids: Open Questions and Future Challenges in Molecular Dynamics Simulations. Chem. Rev. 116, 7078–7116.
[4] Kiselev, A., Bachmann, F., Pedevilla, P., Cox, S.J., Michaelides, A., Gerthsen, D., and Leisner, T. (2017). Active sites in heterogeneous ice nucleation—the example of K-rich feldspars. Science 355, 367–371.
[5] Sosso, G.C., Li, T., Donadio, D., Tribello, G.A., and Michaelides, A. (2016). Microscopic Mechanism and Kinetics of Ice Formation at Complex Interfaces: Zooming in on Kaolinite. J. Phys. Chem. Lett. 7, 2350–2355.
[6] Pandey, R., Usui, K., Livingstone, R.A., Fischer, S.A., Pfaendtner, J., Backus, E.H.G., Nagata, Y., Fröhlich- Nowoisky, J., Schmüser, L., Mauri, S., et al. (2016). Ice-nucleating bacteria control the order and dynamics of interfacial water. Science Advances 2, e1501630.
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2 Program
Day 1 - Tuesday September 18, 2018
Registration and opening words • 9:00 to 13:30 - Registration
• 13:30 to 14:00 - Welcome and Introduction
Session 1: Supercooled Water Chaired by Gabriele C. Sosso
• 14:00 to 14:30 - Hajime Tanaka “Impact of local structural ordering on the anomalies and crystallization of water”
• 14:30 to 14:45 - Discussion
• 14:45 to 15:15 - Christoph Salzmann “New advances in the experimental exploration of water’s phase diagram”
• 15:15 to 15:30 - Discussion
• 15:30 to 16:00 - Coffee Break
• 16:00 to 16:30 – Baron Peters “How trace soluble additives promote homogeneous nucleation”
• 16:30 to 16:45 - Discussion
Open discussion A - Pinpointing the Challenges • 16:45 to 17:15 - Discussion
Day 2 - Wednesday September 19, 2018
Session 2: Water at Interfaces Chaired by Sapna Sarupria
• 9:00 to 9:30 - Paolo Raiteri “Forcefield development for thermodynamically accurate simulations of minerals growth”
• 9:30 to 9:45 - Discussion
• 9:45 to 10:15 – Laurent Joly “Transport properties of interfacial water”
• 10:15 to 10:30 – Discussion
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• 10:30 to 11:00 - Coffee Break
• 11:00 to 11:30 - Matthew Gibson “What I wish you could tell me about ice [Bio-inspired macromolecules for cryopreservation]”
• 11:30 to 11:45 - Discussion
Open discussion B - The Future of Force Fields • 11:45 to 12:15 – Discussion
Lunch • 12:1 5 to 14:00 - Lunch
Session 3: Heterogeneous Ice Nucleation on Model Systems and Inorganic Materials Chaired by Tianshu Li
• 14:00 to 14:30 - Valeria Molinero “Heterogeneous ice nucleation, and beyond”
• 14:30 to 14:45 - Discussion
• 14:45 to 15:15 - Martin Fitzner “Role of structure and dynamics in heterogeneous ice nucleation: insight from model simulations”
• 15:15 to 15:30 - Discussion
• 15:30 to 16:00 - Coffee Break
• 16:00 to 16:30 - Gren Patey “Exploring different factors that influence heterogeneous ice nucleation”
• 16:30 to 16:45 - Discussion
• 16:45 to 17:15 - Alexei Kiselev “Wetting kinetics vs. heterogeneous freezing on graphite and feldspar”
• 17:15 to 17:30 - Discussion
Poster session • 17:30 to 19:30 - Poster Session
Day 3 - Thursday September 20, 2018
Session 4: Heterogeneous Ice Nucleation on Organic Matter - and Clathrate Hydrates
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Chaired by Thomas Koop
• 9:00 to 9:30 - Peter Kusalik “Characterizing key features of the microscopic mechanism of ice nucleation”
• 9:30 to 9:45 - Discussion
• 9:45 to 10:15 - Steve Cox “Formation of methane hydrate in the presence of natural and synthetic nanoparticles”
• 10:15 to 10:30 - Discussion
• 10:3 0 to 11:00 - Coffee Break
• 11:00 to 11:30 - Peter Davies “Are ice-nucleating proteins just big ice-binding proteins?”
• 11:30 to 11:45 – Discussion
• 11:45 to 12:15 - Sapna Sarupria “Molecular simulations studies of hydrates and ice nucleation”
• 12:15 to 12:30 – Discussion
Lunch • 12:30 to 14:00 - Lunch
Session 5: Simulation Methods Chaired by Angelos Michaelides
• 14:00 to 14:30 - Fabio Pietrucci “The important role of collective variables in enhanced sampling simulations of ice nucleation”
• 14:30 to 14:45 - Discussion
• 14:45 to 15:15 - Kurt Binder “The phase coexistence method for the estimation of heterogeneous nucleation barriers”
• 15:15 to 15:30 - Discussion
• 15:30 to 16:00 - Coffee Break
• 16:00 to 16:30 - Ben Slater “Probing the structure versus stability relationship in ices”
• 16:30 to 16:45 - Discussion
• 16:45 to 17:15 - Ying Jiang
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“Probing surface water at sub-molecular level by scanning probe microscopy: from clusters to two-dimensional layers”
• 17:15 to 17:30 - Discussion
Open discussion C - Software Medley: a Open Discussion about How to Further Software Development Throughout e.g. Collaborative Coding • 17:30 to 18:00 - Discussion
Social dinner • 19:30 to 21:30 - Social Dinner
Day 4 - Friday September 21, 2018
Session 6: Bridging the Gap Chaired by Thomas Whale
• 9:00 to 9:30 - Benjamin Murray “Does heterogeneous ice nucleation in the atmosphere matter?”
• 9:30 to 9:45 - Discussion
• 9:45 to 10:15 - Carlos Vega “Homogeneous nucleation of ice. Where are we?”
• 10:15 to 10:30 - Discussion
• 10:30 to 11:00 - Coffee Break
• 11:00 to 11:30 - Jianjun Wang “Bio-inspired Surfaces for Controlling Ice Nucleation”
• 11:30 to 11:45 - Discussion
• 11:45 to 12:15 - Ido Braslavsky “Ice-binding proteins and their interaction with ice crystals”
• 12:15 to 12:30 - Discussion
Open discussion D - Getting Closer to Experiments: an Open Discussion about How to Maximize the Impact of Simulations with respect to Experiments and Applications • 12:30 to 13:00 - Discussion
Closing words • 13:30 to 14:00 - Closing Word
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3 Participant list
Organizers
Sosso, Gabriele Cesare The University of Warwick, United Kingdom Michaelides, Angelos University College London, United Kingdom Li, Tianshu George Washington University, USA
Binder, Kurt - Johannes Gutenberg University Mainz, Germany Borduas, Nadine - ETH Zürich, Switzerland Braslavsky, Ido - The Hebrew University of Jerusalem, Israel Cheng, Bingqing - EPFL, Switzerland Cox, Stephen - University of Cambridge, United Kingdom Davies, Peter - Queen's University, Canada Davies, Michael - Prof. Angelos Michaelides ICE Group, UCL, United Kingdom Fayter, Alice - University of Warwick, United Kingdom Fitzner, Martin - University College London, United Kingdom Flachmüller, Alexander - University of Konstanz, Germany Gibson, Matthew - University of Warwick, United Kingdom Giulia, Galli - University of Chicago, USA Horsch, Martin Thomas - American University of Iraq, Sulaimani, Iraq Joly, Laurent – Université Lyon, France Jedrecy, Alexandre - Sorbonne Université - Université Pierre et Marie, France Jiang, Ying - Peking University, China King, Michael - University of Konstanz, Germany Kiselev, Alexei - Karlsruhe Institute of Technology, Germany Kusalik, Peter - Univ. of Calgary, Canada Liberati, Diego - Consiglio Nazionale delle Ricerche, Italy Määttänen, Anni - Centre National de la Recherche Scientifique, LATMOS, France Mahrt, Fabian - ETH Zürich, Switzerland Molinero, Valeria - University of Utah , USA Murray, Benjamin - University of Leeds, United Kingdom Nezbeda, Ivo - E. Hala Lab of Thermodyn., Acad. Sci. , Czech Republic Nikiforidis, Vasileios-Martin - University of Edinburgh, United Kingdom Ojha, Deepak - University of Paderborn, Germany Pakarinen, Olli - University of Helsinki, Finland Patey, Gren - University of British Columbia, Canada Peters, Baron - University of California, Santa Barbara, USA Pietrucci, Fabio - UPMC - Sorbonne Paris, France Raiteri, Paolo - Curtin University, Perth, Australia Rasti, Soroush - Leiden university, The Netherlands Reischl, Bernhard - INAR / University of Helsinki, Finland Salazar, Marcos - Université de Bourgogne, France Salzmann, Christoph - University College London, United Kingdom Sarupria, Sapna - Princeton University, USA Slater, Ben - University College London, United Kingdom Suh, Donguk - the University of Tokyo, Japan Tanaka, Hajime - The University of Tokyo, Japan Thomson, Erik S. - University of Gothenburg, Sweden
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Vahabpour Roudsari, Golnaz - University of Helsinki, Finland Vega, Carlos - Complutense University of Madrid, Spain Wadhawan, Arjun - University of Amsterdam, The Netherlands Wang, Jianjun - Chinese Academy of Sciences, China Whale, Thomas - University of Leeds, United Kingdom
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4 Talks:
Session 1: Supercooled Water
* Hajime Tanaka Hajime Tanaka, Rui Shi, John Russo, and Flavio Romano Department of Fundamental Engineering, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
Title: "Impact of local structural ordering on the anomalies and crystallization of water"
Abstract: Water displays a vast array of unique properties, known as water's anomalies, whose origin remains subject to debate [1]: on the one hand, thermodynamic anomalies are attributed to criticality associated with a second critical point, while on the other hand, dynamic anomalies are thought to originate from the glass transition singularity. With computer simulations of popular water models, we provide here a unified picture of water's anomalies in terms of locally favored structures [2-6], which are characterized by high tetrahedral and translational symmetries stabilized by four hydrogen bonds [3,4]. Our study indicates a common basic physical origin for thermodynamic and dynamic anomalies [5,6], contrary to the currently popular scenarios mentioned above. We also show that the degree of local structural ordering and its similarity to crystal symmetry are key factors controlling crystal nucleation [2,7-9], which explains why water freezes but silica forms a glass [8].
[1] P. Gallo, et al., Chem. Rev. 116, 7463–7500 (2016). [2] H. Tanaka, Eur. Phys. J E, 35, 113 (2012). [3] J. Russo, & H. Tanaka, Nat. Commun. 5, 3556 (2014). [4] R. Shi and H. Tanaka, J. Chem. Phys. 148, 124503 (2018). [5] R. Shi, J. Russo, and H. Tanaka, to be published. [6] J. Russo, K. Akahane and H. Tanaka, Proc. Natl. Acad. Sci. U. S. A. 115, E3333 (2018). [7] J. Russo, F. Romano, and H. Tanaka, Nature Mater. 13, 733-739 (2014). [8] R. Shi and H. Tanaka, Proc. Natl. Acad. Sci. U. S. A. 115, 1980-1985 (2018). [9] J. Russo, F. Romano, H. Tanaka, Phys. Rev. X (in press).
* Christoph Salzmann Department of Chemistry University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
Title: “New advances in the experimental exploration of water’s phase diagram”
Abstract: Since the days of Bridgman and Tammann, the phase diagram of water has seen a flurry of exciting developments including the discovery of seventeen crystalline polymorphs of ice, the pressure-induced amorphisation of ice I and the existence of at least two distinct amorphous form of ice. In this talk, a variety of new insights into the highly complex behaviour of condensed H2O are presented. Will we ever fully understand H2O? (1) Doping-induced disappearance of ice II from the phase diagram: Ammonium fluoride (NH4F) acts as a ‘magic ingredient’ that enables us to let ice II disappear from the phase diagram in a highly selective fashion.[1] A detailed understanding of the underlying mechanisms and thermodynamics is presented, and we argue that our new finding has wider implications that enables us to understand some of the anomalies of the phase diagram including the anomalous properties of liquid water. The absence of ice II also allows us to study the ice III to ice IX phase transition in great detail which was previously not accessible.
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The selective disappearance of a phase of ice with the aid of a dopant highlights the exciting possibility of potentially discovering new phases of ice in the future using specific dopants. (2) Reorientation dynamics govern the glass transitions of the amorphous ices: The glass transitions of low-density amorphous ice (LDA) and high-density amorphous ice (HDA), and their thermodynamic relationships with the liquid are the topic of controversial discussions. We first show that the glass transition of hydrogen-disordered ice VI is associated with the kinetic unfreezing of molecular reorientation dynamics by measuring the calorimetric 18 responses of the corresponding H2O, H2 O and D2O materials in combination with X-ray diffraction. Well-relaxed LDA and HDA show identical isotopic-response patterns in calorimetry as ice VI, and we conclude that the glass transitions of the amorphous ices are also governed by molecular reorientation processes.[2] This ‘reorientation scenario’ seems to resolve the previously conflicting viewpoints and it is consistent with a fragile to strong transition from the molecular liquid to the amorphous ices. (3) High-density amorphous ice is a ‘derailed’ state along the ice I to ice IV pathway: The structural nature of HDA formed through low-temperature pressure-induced amorphization of ice I is also heavily debated. We show that NH4F I, which is isostructural with ice I, undergoes a very similar pressure collapse upon compression at 77 K compared to ice. This is found for both hexagonal as well as stacking-disordered starting materials. However, the product material is not amorphous but NH4F II, a high-pressure phase isostructural with ice IV. This collapse can be rationalized in terms of a highly effective structural mechanism which we call the Engelhardt-Kamb collapse. In the case of ice I, the orientational disorder of the water molecules leads to a deviation from this mechanism and we therefore classify HDA as a ‘derailed’ state along the ice I to ice IV pathway. DFT calculations suggest that ice XI, i.e. hydrogen-ordered ice I, would indeed not undergo pressure-induced amorphisation but transform to ice IV instead.[3] Overall, a rather crystalline viewpoint of the amorphous ices emerges from our studies both as far as their structures as well as their glass-transition behaviours are concerned.
[1] J.J. Shephard, B. Slater, P. Harvey, M. Hart, C.L. Bull, S.T. Bramwell, C.G. Salzmann, Nat. Phys., 14 (2018) 569–572 [2] J.J. Shephard, C.G. Salzmann, J. Phys. Chem. Lett., 7 (2016) 2281–2285 [3] J.J. Shephard, S. Ling, G.C. Sosso, A. Michaelides, B. Slater, C.G. Salzmann, J. Phys. Chem. Lett., 8 (2017) 1645–1650
* Baron Peters
Title: “How trace soluble additives promote homogeneous nucleation”
Abstract: Trace additives exert control over nucleation and polymorph selection in many natural and industrial environments. We propose a theoretical model that predicts changes in nucleation barriers based on the adsorption properties and concentrations of trace additives. The model is based on classical nucleation theory and a statistical mechanical model for Langmuir adsorption. The model accounts for fluctuating additive coverage and diffusion- controlled attachment kinetics at the nucleus-solution interface. Theoretical predictions closely follow the computational results from a Potts-lattice gas model that includes solvent, solute, and surfactant-like species. We will examine surfactant binding strength, concentration, and oligomerization as ways to modulate the potency and selectivity of additives for controlling nucleation. Finally, we connect the theoretical results to atomistic simulations in a study of SDS additives in methane hydrate nucleation.
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Session 2: Water at Interfaces
* Paolo Raiteri Paolo Raiteri and Julian D Gale Department of Chemistry Curtin University, Perth Western Australia, Australia
Title: “Forcefield development for thermodynamically accurate simulations of minerals growth”
Abstract: Molecular modelling has become an incredibly powerful scientific tool and, thanks to the ever-increasing computational power, researchers are now able to reveal the atomic mechanisms that underpin many complex chemico-physical phenomena. Crystal nucleation and growth is one area where a good phenomenological understanding of the events exists, but there is often a lack of a detailed atomistic picture of the processes and an absence of any predictive tools. As an example, the nucleation processes of minerals are typically described within the framework of Classical Nucleation Theory (CNT), which in many cases predicts nucleation rates several orders of magnitude off the experimentally measured ones. Although it can be argued that the main assumptions of CNT are partially flawed, there is no generally accepted alternative model to describe the process, which can then be used to build a new predictive theory. Here computer simulations can play a pivotal role in validating and developing a new theoretical approach to the growth of minerals. Due to their very low −9 solubility (e.g. Ksp= 3.3×10 for calcite) direct simulations of the nucleation process are still out of reach, but we can infer indirect evidence for what the mechanism could be and extract thermodynamic data for the elementary ion aggregation steps and adsorption on crystals. In this presentation, I will describe our approach to derive thermodynamically accurate forcefields that can be used to describe the ion association and crystal growth for minerals in water. In particular, I will focus on the alkaline earth carbonates and sulphates, as well as on the mineral water interactions, and on their importance in the overall crystal growth process.
* Laurent Joly Institut Lumière Matière Université Lyon 1, France e-mail: [email protected] http://ilm-perso.univ-lyon1.fr/~ljoly/
Title: “Transport properties of interfacial water”
Abstract: Nanofluidic systems (i.e. natural and artificial systems where fluids are confined at the nanoscale) offer alternative and sustainable solutions to problems relating to energy harvesting and water treatment. New behaviors arise in nanoconfined liquids due to the predominant role of surfaces. Indeed, surfaces can limit the performance of nanofluidic devices, through e.g. liquid-solid friction, but they also provide new opportunities to manipulate liquids, through e.g. the so-called osmotic flows, generated at surfaces by non-hydrodynamic forcing (e.g. electric potential gradient: electro-osmosis, solute concentration gradient: diffusio-osmosis, temperature gradient: thermos-osmosis). Here, I will illustrate with recent work how atomistic simulations can help relate the interfacial transport properties of water and aqueous solutions to their equilibrium structure and dynamics. First, I will show how classical and ab initio molecular dynamics simulations can reveal the molecular mechanisms of liquid- solid friction, controlling the hydrodynamic boundary condition. In particular, I will show that the commonly accepted relation between wetting and friction can fail in the case of water on graphene and boron nitride, and that the electronic structure of the interface plays a critical role on friction in these systems [1,2]. I will also explain why adding a very small amount of
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alcohol in water can dramatically decrease interfacial friction [3]. I will then discuss how osmotic flows depend on both interfacial structure and dynamics, taking as examples electro- osmotic flows in foam films [4,5], diffusio-osmotic flows of water-alcohol mixtures [6], and thermo-osmotic flows on graphitic walls [7,8].
[1] G. Tocci, L. Joly, A. Michaelides: “Friction of water on graphene and hexagonal Boron Nitride from ab initio methods: very different slippage despite very similar interface structures”, Nano Lett. 14, 6872 (2014) [2] L. Joly, G. Tocci, S. Merabia, A. Michaelides: “Strong coupling between nanofluidic transport and interfacial chemistry: how defect reactivity controls liquid-solid friction through hydrogen bonding”, J. Phys. Chem. Lett. 7, 1381 (2016) [3] S. Nakaoka, Y. Yamaguchi, T. Omori, L. Joly: “Molecular Dynamics Analysis of the Friction between a Water-Methanol Liquid Mixture and a Non-Polar Solid Crystal Surface”, J. Chem. Phys., 146, 174702 (2017) [4] L. Joly, F. Detcheverry, A.-L. Biance: “Anomalous zeta potential in foam films”, Phys. Rev. Lett. 113, 088301 (2014) [5] A. Barbosa de Lima, L. Joly, “Electro-osmosis at surfactant-laden liquid-gas interfaces: beyond standard models”, Soft Matter 13, 3341 (2017) [6] C. Lee, C. Cottin-Bizonne, R. Fulcrand, L. Joly, C. Ybert: “Nanoscale Dynamics versus Surface Interactions: What Dictates Osmotic Transport”, J. Phys. Chem. Lett. 8, 478 (2017) [7] L. Fu, S. Merabia, L. Joly: “What controls thermo-osmosis? Molecular simulations show the critical role of interfacial hydrodynamics”, Phys. Rev. Lett. 119, 214501 (2017) [8] L. Fu, S. Merabia, L. Joly: “Understanding Fast and Robust Thermo-Osmotic Flows through Carbon Nanotube Membranes: Thermodynamics Meets Hydrodynamics”, J. Phys. Chem. Lett. 9, 2086 (2018)
* Matthew Gibson Department of Chemistry and Warwick Medical School University of Warwick, UK, CV4 7AL [email protected] www.warwick.ac.uk/go/gibsongroup @LabGibson
Title: “What I wish you could tell me about ice [Bio-inspired macromolecules for cryopreservation]”
Abstract: Antifreeze (aka ice-binding/structuring) and ice nucleating proteins have many desirable properties for modulating ice growth/formation, but they are often not suitable for application, where scale-up, tuneability, immunogenicity and stability must be considered. We have introduced the concept of using synthetic macromolecules (polymers) to mimic antifreeze proteins and have applied these to challenging problems in cryopreservation. However, the rational design of these is complicated by the gaps in our knowledge of how native proteins function on the molecular scale, and if our polymer mimics even function by the same mechanisms. E.g., just because they have related macroscopic properties, does this mean they interact with ice in the same way? Here I will summarise our progress in developing synthetic mimics of antifreeze proteins, particularly those which can inhibit ice recrystallisation, for application in cryobiology. The role of the chemical functionality will be discussed, and if certain groups (e.g. hydroxyls) are essential (our answer = no) or if structural features, in particular amphipathy is the crucial motif. I will also discuss what constitutes ‘active’ – a high enough concentration of anything will slow ice crystal growth, and some emerging macromolecules appear to be potent cryoprotectants but do not interact with ice strongly. Therefore critical discussion about the magnitude of observed effects is important. Finally, I will try to direct which questions/answers an experimentalist would like from theory/modelling to help drive this field forward.
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Session 3: Heterogeneous Ice Nucleation on Model Systems and Inorganic Materials
* Valeria Molinero Department of Chemistry The University of Utah, 315 South 1400 East, Salt Lake City, United States
Title: “Heterogeneous ice nucleation, and beyond”
Abstract: The crystallization of water is one of the most ubiquitous phase transitions on Earth, where it plays a key role in the control of climate and precipitation. In the absence of surfaces that “catalyze” the phase transformation, water forms ice only when cooled below about - 38oC. However, a variety of atmospheric aerosols and organic surfaces promote the nucleation of ice at warmer temperatures. Among these, ice-nucleating proteins are the most efficient. In this presentation I will discuss our work using molecular simulations and theory to elucidate the molecular mechanisms of nucleation of ice and how it is “catalyzed” by a variety of molecules and surfaces, and how to use this understanding to design surfaces that can nucleate ice without supercooling.
* Martin Fitzner Thomas Young Centre, London Centre for Nanotechnology and Department of Physics and Astronomy University College London, Gower Street, London WC1E 6BT, United Kingdom
Title: “Role of Structure and Dynamics in Heterogeneous Ice Nucleation: Insight from Model Simulations”
Abstract: From intracellular freezing, to the enormous extent of glaciers to the whole of the water cycle depending on ice nucleation in clouds – the freezing of water is ubiquitous and shapes life as we know it. The initial spark that causes supercooled liquid water to transform into ice often originates at impurities that are in contact with the liquid (i.e. heterogeneously). This poses a challenge for experiments as there is wide variety of materials combined with time and length scales that are difficult to access. Thus, model simulations in the computer are a useful tool to further our microscopic understanding of the ice nucleation process. In this work we present results from two projects that each deal with one of the two key players regarding any ordering process: First, we examine the role of the structure of a substrate and its ability to enhance the ice nucleation process [1,2,3,4]. We study a large variety of different model substrates combined with statistical learning techniques and find for instance that one of the most prominent text book requirements – the so-called lattice match – is not sufficient to predict the ice nucleation ability in general. Second, we investigate the role of liquid dynamics [5]. Contrary to the liquid/substrate structure this aspect has not received much attention in the literature and is mostly neglected in theoretical modelling. As a first step, we probe a homogeneous system by uncovering mobile and immobile regions with molecular resolution. We analyze the structure of the resulting domains and find that ice clusters are born within immobile regions after a substantial dynamical incubation period.
[1] M Fitzner, GC Sosso, SJ Cox, and A Michaelides, 2015. J. Am. Chem. Soc., 137(42), pp.13658-13669. [2] M Fitzner, GC Sosso, F Pietrucci, S Pipolo, and A Michaelides, 2017. Nat. Commun. 8(1), p.2257. [3] M Fitzner, P Pedevilla and A Michaelides, in preparation. [4] P Pedevilla, M Fitzner and A Michaelides, 2017. Physical Review B 96(11), p. 115441. [5] M Fitzner, GC Sosso, SJ Cox, and A Michaelides, submitted.
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* Gren Patey Department of Chemistry University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
Title: “Exploring Different Factors that Influence Heterogeneous Ice Nucleation”
Abstract: Direct, classical, molecular dynamics simulations of heterogeneous ice nucleation by various models for solid ice nuclei will be discussed. Nuclei considered will include (possibly among others) AgI, kaolinite, gibbsite, and feldspar. It is known from recent simulation and experimental investigations that at least a few different factors can have important influences on heterogeneous ice nucleation. These include properties of both the ice nucleus, and of the solution from which ice is nucleating. The lattice structure of the nucleus, the atomic level structure of the surface(s) exposed to solution, as well as the distribution of surface charge (electric fields) have all been identified as factors that can strongly influence the ice nucleating ability of a particular ice nucleus, or of a particular surface. Attention will be focussed on the relative importance of these factors, and how they can act to enhance or oppose ice nucleation in different systems and situations. Experiments have also shown that salt concentration can have a strong influence on ice nucleation from solution. Simulations aimed at understanding the microscopic origin of salt effects will also be described.
* Alexei Kiselev Alexei Kiselev, Nadine Tüllmann, Michael Koch, and Thomas Leisner Atmospheric Aerosol Research Department, Institute for Meteorology and Climate Research Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
Title: “Wetting kinetics vs. heterogeneous freezing on graphite and feldspar”
Abstract: Freezing of supercooled water in contact with a foreign substrate can be facilitated by the presence of the so-called “Ice Nucleating Active Sites” (INAS), the special sites on the surface of the substrate where the energy required for the formation of the critical ice embryo is reduced. Under stationary conditions, the probability of freezing can be described in the framework of the Classical Nucleation Theory, taking into account the properties of the INAS sites and stochastic nature of nucleation. Recent progress in atomistic modeling and experimental research allowed for a significant progress in the quantitative description of heterogeneous ice nucleation. However, under non-equilibrium conditions, the freezing mechanism becomes more complicated. Such conditions can be encountered, for example, in a contact nucleation, where a supercooled droplet collides with an ice nucleating particle or substrate. Depending on the hydrophilic properties of the substrate surface, a droplet would require some time to achieve a stable equilibrium on the substrate (dynamic wetting). During this transition period, freezing kinetics can be influenced by the changing properties of the water-substrate interface. In this contribution, we report experimental measurements of supercooled droplets freezing upon contact with the precooled flat surfaces of freshly cleaved feldspar and graphite. We explore the competition between dynamic wetting and freezing kinetics by recording the freezing-upon-collision events with a high-speed video camera. We report the measurements of the average time needed to initiate freezing for different types of ice nucleating particles and temperature ranges. Surprisingly, this characteristic time delay does not correlate with the contact freezing efficacy of the ice nucleating particles, nor does it show a strong correlation with the area of the water-substrate interface. Additionally, we report only negligible enhancement of ice nucleation by graphite substrate. Finally, we discuss possible mechanisms of such freezing behavior and potential implications for future ice nucleation research.
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Session 4: Heterogeneous Ice Nucleation on Organic Matter - and Clathrate Hydrates
* Peter Kusalik Department of Chemistry University of Calgary, 2500 University drive NW, Calgary, Alberta T2N 1N4, Canada
Title: “Characterizing Key Features of the Microscopic Mechanism of Ice Nucleation”
Abstract: The ordering processes associated with the nucleation and growth of ice crystals have proven difficult to study directly with experiments, in part due to their stochastic nature of the underlying molecular processes. Molecular simulations, while affording an excellent opportunity to investigate crystal nucleation and growth of ice at a molecular level, have also presented many challenges. Consequently, a complete molecular-level picture of the factors important in ice formation has yet to emerge. In this presentation I will begin with a brief introduction of some key issues around molecular simulations of crystallization, focusing on some attributes and limitation of models and methods relevant to ice nucleation. I will also review some of the approaches that have been developed and utilized for detecting order in the simulation of systems during ice formation. While specific results from molecular simulations exploring ice nucleation will be a focus, the nucleation of gas clathrate hydrates will also be examined and compared. I will present results that will demonstrate that the process of crystallization is characterized by collective phenomena involving many molecules, where the organization can be seen to occur in stages. I will also show that defects can play key roles in observed behaviours, where the lifetimes and transitions of specific structures will be discussed. To help provide insights into their phenomenological similarities and differences, I will consider how rugged funnel-shaped potential energy landscapes can provide a lens for understanding key aspects and features of nucleation in ice and gas hydrates.
* Stephen Cox Department of Chemistry University of Cambridge, Cambridgeshire CB2 1EW, United Kingdom
Title: “Formation of methane hydrate in the presence of natural and synthetic nanoparticles”
Abstract: Natural gas hydrates occur widely on the ocean-bed and in permafrost regions, and have potential as an untapped energy resource. Their formation and growth, however, poses major problems for the energy sector due to their tendency to block oil and gas pipelines, while their melting is viewed as a potential contributor to climate change. Although recent advances have been made in understanding bulk methane hydrate formation, the effect of impurity particles, which are always present under conditions relevant to industry and the environment, remains an open question. Here I will present results from neutron scattering experiments and molecular dynamics simulations that show that the formation of methane hydrate is insensitive to the addition of a wide range of impurity particles. Analysis of both the experimental and simulation results shows that this is due to the different chemical natures of methane and water, with methane generally excluded from the volume surrounding the nanoparticles. This has important consequences for our understanding of the mechanism of hydrate nucleation and the design of new inhibitor molecules.
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* Peter Davies Peter L. Davies and Virginia Walker Queen’s University, Kingston, Canada
Title: “Are ice-nucleating proteins just big ice-binding proteins?”
Abstract: Ice-binding proteins (IBPs) and ice-nucleating proteins (INPs) have opposing functions. IBPs serve as antifreezes or inhibitors of ice recrystallization since they constrain ice growth by binding at intervals over the ice crystal surface. As antifreezes, IBPs lower the solution freezing point. In contrast, INPs initiate the formation of ice at high sub-zero temperatures. Despite these opposite roles it has been suggested that the two proteins may have similar structure-function relationships. At the level of structure, the central repetitive nucleating region of INPs has been modeled as a beta-solenoid, which is also the most common fold amongst IBPs. The mechanism by which IBPs bind to ice could be through the organization of ice-like waters (anchored clathrate waters) by their ice-binding sites. These ice-like waters can merge with, and freeze to, the quasi-liquid layer of water between the ice lattice and bulk water, thereby freezing the IBP to ice. Increasing the size of the ice-binding site in IBPs improves ice adsorption, presumably by increasing the number of ice-like waters available for binding. By extrapolation, the organization of very large numbers of ice-like waters on an INP surface might become the nucleus for ice formation and rapid growth. Here we will present new examples of ice-like waters on IBP ice-binding sites. We will describe de novo attempts to make IBPs out of non-ice-binding proteins, and review attempts to convert IBPs into INPs by multiplexing them, and to make IBPs by shrinking the repetitive INP region.
Funded by the Canadian Institutes of Health Research and the Natural Sciences and Engineering Research Council
Session 5: Simulation Methods
* Fabio Pietrucci Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie Sorbonne Universités - Université Pierre et Marie Curie Paris 6, F-75005 Paris, France.
Title: “The important role of collective variables in enhanced sampling simulations of ice nucleation”
Abstract: Several simulation methods can be applied to study ice nucleation, with the aim of reconstructing the mechanism, free energy landscape, and kinetic rates. In many of these techniques, collective variables able to track the structural transition in atomic detail play an important role during the simulation and/or in the analysis of results [1]. We recently introduced new collective variables based on the adjacency matrix that track changes of topology of interatomic networks. Thanks to a general formulation, the variables can be applied to many different materials. Combining them with enhanced sampling methods like metadynamics and umbrella sampling, we demonstrated the possibility to systematically simulate transitions among liquid, amorphous, and crystalline forms throughout the phase diagram of water, at a cheap computational cost [2]. In particular, the crystallization of liquid and amorphous water can be achieved without the help of supercooling, and without the need of an educated guess about the transition mechanism. Application of the same technique to the freezing of water in contact with different model surfaces allowed to detect deviations from heterogeneous classical nucleation theory [3]. The next logical step, the systematic simulation of ice nucleation at different conditions and on different materials, described with as-accurate- as-possible force fields, might be within reach.
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[1] F. Pietrucci, Rev. Phys. 2, 32 (2017) [2] S. Pipolo, M. Salanne, G. Ferlat, S. Klotz, A.M. Saitta, F. Pietrucci, Phys. Rev. Lett. 119, 245701 (2017) [3] M. Fitzner, G.C. Sosso, F. Pietrucci, S. Pipolo, A. Michaelides, Nat. Commun. 8, 2257 (2017)
* Kurt Binder Kurt Binder [1], Subir K.Da s[2], Fabian Schmitz [1], Andreas Troester [3], Peter Virnau [1],and David Winter [1] 1) Institut fuer Physik Johannes Gutenberg Universitaet Mainz,Staudinger Weg 7, D-55099 Mainz,Germany 2) Theoretical Sciences Unit J.Nehru Centre for Advanced Scientific Research, Jakka, Bangalore, 56004 India 3) Institute for Materials Chemistry Vienna University of Technology, Getreidemarkt 9,A-1060 Vienna, Austria
Title: “The phase coexistence method for the estimation of heterogeneous nucleation barriers”
Abstract: When a small liquid droplet coexists with surrounding vapor in a (closed) finite volume in equilibrium, excess quantities relative to bulk phase coexistence (excess density, chemical potential, free energy ) yield information on the droplet volume and surface excess free energy, without the need to characterize the droplet surface and its shape explicitly. When one accounts for the translational entropy of the droplet in the volume [1], the curvature dependence of the droplet surface free energy can be quantified: in d=2 dimensions the leading term is logarithmic, while in d=3 it is of the Tolman form. This concept can be generalized to a wall attached droplet in a volume L x L x D , but the droplet can only move on the substrate area L x L , and hence the translational entropy correction now is of the order ln (L x L).The nucleation barrier against heterogeneous nucleation can be estimated, without the need of assuming a sphere-cap shape of the droplet [2]. If, however, one makes this sphere-cap assumption, the dependence of the contact angle on droplet radius can be obtained. For the lattice gas model as well as for a symmetric Lennard-Jones mixture, it can be interpreted in terms of a negative line tension[2]. The extension of these concepts to the nucleation of crystals is briefly mentioned.
[1] A.Troester, F.Schmitz, P.Virnau, K.Binder, J.Phys.Chem.B122(2018) 3407 . [2] S.K.Das, S.A.Egorov, P.Virnau, D.Winter, K.Binder, J.Phys.:Cond.Matter (2018) accepted.
* Ben Slater Department of Chemistry University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
Title: “Probing the structure versus stability relationship in ices”
Abstract: As one approaches coexistence, nucleation rates of first order phase transitions diverge, because the thermodynamic driving force that favors one phase over the other disappears. In finite systems, however, transitions between coexisting phases can still occur as in this case the nucleation barrier remains finite. For systems simulated with periodic boundaries one also knows the transition states, which are slab-like and can be easily employed to generate reactive trajectories. Using the magnetization reversal in the Ising
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model as well as the freezing/melting and evaporation/condensation of water as examples, we discuss what can be learned from such trajectories at coexistence about the nucleation mechanism off-coexistence. While the shapes of larger clusters in such trajectories are artifacts of the periodic boundary conditions, the morphologies of small clusters obtained at and away from coexistence are comparable. This equivalence holds up to cluster sizes that can be estimated from a simple scaling relation for the touching probability of diffusing interfaces.
Joint work with Clemens Moritz, Marcello Sega and Phillip L. Geissler
* Ying Jiang International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, P. R. China Email: [email protected]
Title: “Probing surface water at submoleuclar level by scanning probe microscopy: from clusters to two-dimensional layers”
Abstract: Water at surfaces is ubiquitous in nature and plays an essential role in a broad spectrum of physics, chemistry, biology, energy and material sciences. One of the most fundamental issues is the characterization of H-bonding structure and related dynamics during the intial stage of water/ice growth. Ideally, attacking this problem requires the access to the internal degrees of freedom of water molecules, i.e. the directionality of OH bonds. However, it remains a great challenge due to the small size of hydrogen. In this talk, I will present our recent progress on the development of new-generation scanning probe microscopy/spectroscopy (SPM/S) with ultrahigh sensitivity and resolution, and its application to surface water. I will first focus on how to achieve submolecular-resolution imaging and single-bond vibrational spectroscopy of single water molecules via controlling tip-water coupling. In the following, I will discuss the application of those techniques to water clusters, ion hydrates and two-dimensional ice layers on insulating and metal surfaces. Some important issues, including H-bonding topology, proton dynamics, nuclear quamtum effects (NQEs), ion transport, atomic defects and edge structures, will be addressed. The experimental results are substantiated by ab initio density functional theory (DFT) calculations and classical molecular simulations (MD).
Session 6: Bridging the Gap
* Benjamin J. Murray Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
Title: “Does heterogeneous ice nucleation in the atmosphere matter?”
Abstract: For many years it has been argued that heterogeneous nucleation of ice is important for clouds and climate. However it is one of many uncertain cloud processes, so how important is it? The answer, for some cloud types, is it matters a great deal, whereas in others the answer is more subtle. In this presentation I will review our recent work were we have clearly demonstrated that heterogeneous ice nucleation is of first order importance in shallow clouds over the Southern Ocean [Vergara-Temprado et al., 2018]. These clouds are extremely sensitive to ice nucleating particle concentrations and cloud systems the size of Western Europe can be removed from the atmosphere in the presence of ice nucleating particles. The impact of ice nucleating particles on this particular cloud types dwarfs the impact
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of other variables, such as the concentration of aerosol which trigger liquid droplet formation. In addition, I will review our understanding of which aerosol types are thought to be of first order importance to the global ice nucleating particle population and end with a summary of what we do not know and how our lack of a fundamental understanding of heterogeneous ice nucleation limits our predictive capacity.
Vergara-Temprado, J., A. K. Miltenberger, K. Furtado, D. P. Grosvenor, B. J. Shipway, A. A. Hill, J. M. Wilkinson, P. R. Field, B. J. Murray, and K. S. Carslaw (2018), Strong control of Southern Ocean cloud reflectivity by ice-nucleating particles, P. Natl. Acad. Sci. USA, doi:10.1073/pnas.1721627115.
* Carlos Vega Departamento de Química Física, Facultad de Ciencias Químicas Universidad Complutense de Madrid, 28040 Madrid, Spain
Title: “Homogeneous nucleation of ice. Where are we?”
Abstract: In the last years there has been an increasing interest in determining the homogeneous nucleation rate of ice. On the experimental side, several groups have determined the homogeneous nucleation rate of ice in the low temperature range (i.e below 230K )[1,2]. The results from different groups are different and it would be useful to understand why this is the case. Also the growth rate of ice has been measured experimentally [3]. On the simulation side there have been also a number of papers dealing with the nucleation of ice at room and high pressures. In this presentation I will discuss the results obtained in the last years including results for the nucleation of ice in salty water [4,5]. It will be shown that the interfacial free energy is the key parameter to understand the nucleation of ice. Finally some general remarks will be given on the time it takes to freeze water and the impact of this on the possible existence of a liquid-liquid transition in supercooled water [6].
[1] H.Laksmono et al., J.Phys.Chem.Lett., 6, 2826, (2015) [2] A.J. Amaya and B.E. Wyslouzil, J.Chem.Phys., 148, 084501, (2018) [3] Y. Xu, N.G. Petrik, R.S. Smith, B.D. Kay, and G.A. Kimmel, PNAS , 113, 14921, (2016) [4] G.D.Soria, J.R.Espinosa, J.Ramirez, C.Valeriani, C.Vega and E.Sanz, J.Chem.Phys. , 148, 222811 (2018) [5] J.R.Espinosa et al., Phys. Rev. Lett. , 117 , 135702, (2016) [6] J.R.Espinosa,C.Navarro,E.Sanz,C.Valeriani and C.Vega, J.Chem.Phys. 145 211922 (2016)
* Jianjun Wang Institute of Chemistry University of Chinese Academy of Sciences, Beijing, P. R. China
Title: “Bio-inspired surfaces for controlling ice nucleation”
Abstract: Understanding and controlling ice nucleation are of great importance in both fundamental research and practical applications. However, our understanding of ice nucleation is far from satisfactory. Nature has unique ways in regulating ice formation, for example, antifreeze proteins (AFPs) protect organisms from freezing damage by regulating ice formation via controlling the arrangement of hydroxyl groups. In this talk, I will first discuss our investigation into the fundamentals of AFPs in regulating ice nucleation via revealing the Janus effect of AFPs on ice nucleation. We found the properties of the interfacial water are essential for AFPs in controlling ice nucleation. Inspired by AFPs, we have synthesized a
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series of model surface materials for regulating ice nucleation, which in turn consolidates that interfacial water is essential for regulating ice nucleation.
* Ido Braslavsky The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel. [email protected] http://www.agri.huji.ac.il/~braslavs/
Title: “Ice-binding proteins and their interaction with ice crystals”
Abstract: We are investigating the interactions of ice-binding proteins IBPs with ice surfaces. In particular, we investigate the dynamic nature of the protein&ice interaction using fluorescence microscopy techniques combined with temperature-controlled microfluidic devices. The results show that binding of IBP to ice is irreversible and that the freezing temperature depression is sensitive to the time allowed for the proteins to accumulate on ice surfaces. This time sensitivity changes dramatically between different types of IBPs. Our results relate the dynamics and level of activity of various types of IBPs to their ability to bind to specific ice orientations, in particularly to the basal plane of the ice. The binding of IBPs to ice crystals is mediated via their interaction with water molecule network that surrounds the proteins. These interaction, and their potential source for heterogeneous ice nucleation will be discussed. The results that will be presented contribute to an understanding of the mechanisms by which IBPs act. Such understanding is critical for the successful use of IBP in cryobiological applications.
Supported by the European-Research-Council (ERC), the National-Science-Foundation (NSF), and the Israel-Science-Foundation (ISF).
References: - Falling Water Ice Purification Affinity Purification of Ice Binding Proteins, C Adar et al., Scientific Reports, 2018 - Protein-Water-Ice Contact Angle, JOM Karlsson, I. Braslavsky, and JAW Elliott, Langmuir. 2018 - Structure of a bacterial ice binding protein with two faces of interaction with ice. M.Mangiagalli, et al. FEBS 2018 - Ice-Binding Proteins and Their Function, M. Bar-Dolev, I. Braslavsky, and P.L. Davies, Ann. Rev. Biochem. 2016 - Ice-Binding Proteins that Accumulate on Different Ice Crystal Planes Produces Distinct Thermal Hysteresis Dynamics, Drori, R., et al., R. Soc. Interface 2014. - LabVIEW-operated Novel Nanoliter Osmometer for Ice Binding Protein Investigations, I. Braslavsky and R Drori, Journal of Visualized Experiments 2013. - Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth, Y Celik et al. PNAS 2013. - Superheating of ice crystals in antifreeze protein solutions, Y Celik et al. PNAS 2010.
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5 Posters:
* Bingquing Cheng Bingqing Cheng (1), Gareth Tribello (2) and Michele Ceriotti (1).
(1) École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland (2) Queen’s University Belfast, Belfast, UK
Title: "Bridging the gap between atomistic and macroscopic models of homogeneous nucleation"
Abstract: Nucleation has many implications in science and technology, including metal casting, the assembly of microtubules in cells, and the formation of water droplets in the atmosphere. Because the experimental investigation of dynamical nucleation processes is very difficult, much attention has been paid to atomistic simulation efforts in the last two decades. However, atomistic simulation studies of nucleation face two major challenges. Firstly, the free energy barrier separating the metastable phase and the stable phase can be very high, making nucleation times much larger than the time scales accessible to molecular dynamics simulations. Secondly, it is highly non-trivial to develop a predictive macroscopic model of nucleation using the microscopic quantities directly obtained from atomistic simulations. In this talk, I aim to address the aforementioned difficulties. I will first briefly introduce state- of-the-art enhanced sampling methods for atomistic simulations, and their applications to studying homogeneous nucleation. I will then discuss our latest thermodynamic model that links macroscopic theories and atomic-scale simulations and thus provide a simple and elegant framework to verify and extend classical nucleation theory.
[1] B. Cheng, G. A. Tribello, M. Ceriotti, Physical Review B 92 (18), 180102 (2015). [2] B. Cheng, M. Ceriotti, The Journal of chemical physics 146 (3), 034106 (2017). [3] B. Cheng, G. A. Tribello, M. Ceriotti, The Journal of chemical physics 147 (10), 104707 (2017). [4] B. Cheng, M. Ceriotti, arxiv: 1803.09140 (2018).
* Nadine Borduas-Dedekind Nadine Borduas-Dedekind1,2, Sophie Bogler2, Killian Brennan1, Robert O. David1, Kristopher McNeill2, Zamin A. Kanji1
1 Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland 2 Institute for Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland University
Title: "Organic aerosols as ice nucleating particles in immersion freezing mode"
Abstract: Organic aerosols represent a subset of atmospheric particles able to act as cloud condensation nuclei (CCN) and, as more recently found, ice nucleating particles (INPs). CCN and INPs affect the ratio of water and ice in mixed-phase clouds, leading to an impact on Earth’s radiative balance. In this work, we use dissolved organic matter (DOM) as a proxy for organic aerosols and lake spray aerosols in ice nucleation experiments. DOM is a complex mixture of organic matter, proteinaceous material, humic-like substances, lignin, organic acids and some ions. As the dominant IN mechanism in mixed-phase clouds is immersion freezing, we investigated the ability of DOM to act as INPs, using our homebuilt immersion freezing
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setup DRoplet Ice Nucleation Counter Zurich (DRINCZ). We use field collected DOM from American rivers and find that the DOM, despite coming from different locations, shows consistent freezing of 50% of the frozen fraction around –12 °C. We are now working on identifying the material within DOM responsible for its INP activity. Preliminary results suggest the importance of lignin as well as proteinaceous material. Current work includes testing discrete organic molecules in the hope to identify the smallest ice active organic molecule. In all, we hope to present a laboratory-based chemical perspective to the ability of organic matter to nucleate ice in the atmosphere.
* Alice E.R. Fayter Alice E. R. Fayter *a, Rebecca A. Stevens a Józef R. Lewandowski a, Matthew I. Gibson a,b aDepartment of Chemistry, University of Warwick, Coventry, CV4 7AL, UK bWarwick Medical School, University of Warwick, Coventry, CV4 7AL, UK *[email protected]
Title: "Characterisation of the Effects on Ice Nucleation, Morphology and Growth upon Addition of Ice-active Compounds; a Biophysical Study"
Abstract: Some abstract Ice crystal formation and growth is a serious problem for many different fields, including food science, mechanical engineering, agriculture, and cryobiology, and yet, despite being one of the most studied materials on Earth, there is still an incomplete understanding of its properties. Ice can damage crops, reduce the performance of aircrafts and reduce cell viability during cryopreservation. The need to increase our physical understanding of ice and how it is affected by ice-active molecules is fundamental to improving techniques for preventing ice formation. By employing physical, biological and chemical principles this work explores extremophile survival by examining the effect of different compounds including antifreeze proteins (AFPs), polymer mimics and small molecules, on ice morphology and growth, with the aim of elucidating mechanisms of action and enabling the production of more active, less toxic polymer mimics of biomacromolecular antifreezes. By understanding the mechanism of ice growth, we can potentially control it, thus providing the opportunity to improve techniques used to observe ice growth, as well as having a focus for future ice nucleants and cryoprotectants. The ice growth process and the mechanism of action of ice recrystallization inhibition (IRI) active compounds are investigated, with the goal of characterising ice structures and how they are affected by these compounds. A range of methods including solid state NMR and X- ray diffraction are used to aid characterisation and analysis by monitoring structural changes such as Ostwald ripening and the cryoprotectants-ice interface. The results show the potential in using these techniques to further elucidate the mechanism of action of ice-active compounds as well as in pure ice growth itself.
1. Gibson, M. I. Slowing the growth of ice with synthetic macromolecules: beyond antifreeze(glyco) proteins. Polym. Chem. 1, 1141 (2010). 2. Voets, I. K. From ice-binding proteins to bio-inspired antifreeze materials. Soft Matter 13, 4808–4823 (2017). 3. Olijve, L. L. C. et al. Blocking rapid ice crystal growth through nonbasal plane adsorption of antifreeze proteins. Proc. Natl. Acad. Sci. 113, 3740–3745 (2016). 4. Biggs, C. I. et al. Polymer mimics of biomacromolecular antifreezes. Nat. Commun. 8, 1546 (2017). 5. Siemer, A. B. & Mcdermott, A. E. Solid-State NMR on a Type III Antifreeze Protein in the Presence of Ice Solid-State NMR on a Type III Antifreeze Protein in the Presence of Ice. 130, 17394–17399 (2008).
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* Alexander Flachmüller Alexander Flachmüller, Christina Rank, Stefan Mecking, Christine Peter.
Department of Chemistry University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany Title: " Coarse grained simulation of polymer nanocrystal formation in aqueous solution"
Abstract: The crystallinity of polyolefins can be used as a structure forming principle to generate nanoparticles of highly defined lamellar thickness and hexagonal shape. By functionalizing the polyolefins at precisely spaced distances, nanoparticles with particularly uniform structural properties are obtained with very interesting new opportunities in the field of self-assembly. Classical organic chemistry might be utilized to introduce or change functionality and thus modify particle behaviour. Experiments have shown that bifunctionalized alkanes are able to form similar nanoparticles compared to polymers [1,2]. Specific tailoring of particle behaviour however requires a molecular understanding of the interplay of different driving force. To better understand this interplay, coarse-grained molecular dynamics simulations of the self-assembly of bifunctionalized alkanes and short polymers in aqueous solution were performed. The focus was to systematically vary chain length as well as interaction parameters of the functional groups and investigate how these properties affect nucleation, growth and also shape and internal order of the nanoparticles.
References: [1] Mecking, S. ; Witt, T. ; Häußler, M. ; Kulpa, S. ; Angew.Chem. Int. Ed. 2017, 56,7589– 7594 [2] Mecking, S. ; Ortmann, P. ; Trzakowski, J. ; Krumova, M. ; ACS Macro Lett. 2013, 2, 125−127
* Martin Horsch K. Langenbach1,a), M. Heilig2, M. Horsch1, and H. Hasse1 1Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Kaiserslautern D- 67663, Germany 2ROM, Digitalization in Research and Development, BASF SE, Ludwigshafen D-67056, Germany
Title: "Study of homogeneous bubble nucleation in liquid carbon dioxide by a hybrid approach combining molecular dynamics simulation and density gradient theory"
Abstract: A new method for predicting homogeneous bubble nucleation rates of pure compounds from vapor-liquid equilibrium (VLE) data is presented. It combines molecular dynamics simulation on the one side with density gradient theory using an equation of state (EOS) on the other. The new method is applied here to predict bubble nucleation rates in metastable liquid carbon dioxide (CO2). The molecular model of CO2 is taken from previous work of our group. PC-SAFT is used as an EOS. The consistency between the molecular model and the EOS is achieved by adjusting the PC-SAFT parameters to VLE data obtained from the molecular model. The influence parameter of density gradient theory is fitted to the surface tension of the molecular model. Massively parallel molecular dynamics simulations are performed close to the spinodal to compute bubble nucleation rates. From these simulations, the kinetic prefactor of the hybrid nucleation theory is estimated, whereas the nucleation barrier is calculated from density gradient theory. This enables the extrapolation of molecular simulation data to the whole metastable range including technically
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relevant densities. The results are tested against available experimental data and found to be in good agreement. The new method does not suffer from typical deficiencies of classical nucleation theory concerning the thermodynamic barrier at the spinodal and the bubble size dependence of surface tension, which is typically neglected in classical nucleation theory. In addition, the density in the center of critical bubbles and their surface tension is determined as a function of their radius. The usual linear Tolman correction to the capillarity approximation is found to be invalid.
* Alexandre Jedrecy Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie Sorbonne Universités - Université Pierre et Marie Curie Paris 6, F-75005 Paris, France. Title: "Enhanced sampling simulations of ice nucleation based on topological path collective variables"
Abstract: We present molecular dynamics simulations of ice nucleation based on realistic interatomic potentials. Our simulations exploit enhanced sampling techniques like metadynamics and umbrella sampling in combination with recent collective variables capturing topological changes as described by the adjacency matrix of interatomic connections [1].
The definition of the variables requires only to specify the structure of the end states, namely water and ice, and allow to discover transition pathways without the need of an educated guess [2]. Our objective is to reconstruct the nucleation mechanism, free energy landscape and kinetic rates. We focus on the homogeneous case, however we also present preliminary results on heterogeneous nucleation.
[1] G.A. Gallet and F. Pietrucci Structural cluster analysis of chemical reactions in solution J. Chem. Phys. 139, 074101 (2013) [2] S. Pipolo, M. Salanne, G. Ferlat, S. Klotz, A.M. Saitta, F. Pietrucci Navigating at will on the water phase diagram Phys. Rev. Lett. 119, 245701 (2017)
* Michael King Michael King and Christine Peter Department of Chemistry University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
Title: "Coarse-grained simulation models to study nucleation and growth of calcium minerals"
Abstract: Fundamental systems to study nucleation and crystallization are calcium based minerals such as calcium carbonates or phosphates which are found in bones, teeth, shells or are used as building materials. Due to the rare event character of nucleation, the different dimensions of pre- and postnucleation stages and possible non-classical nucleation pathways, the investigations require a range of simulation techniques and sampling methods. In the context of a multi-resolution framework to investigate the nucleation and growth of calcium minerals, we have developed a particle based coarse-grained (CG) model for calcium carbonate. The model relies on the monoatomic water model by Molinero [1] and additional three-body interactions to reproduce properties of the solid mineral phases as well as the constituents in solution. We can show how differently tuned CG model parameters affect the crystallization pathways by stabilizing different intermediates - spanning a wide range of
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degrees of crystallinity and water content. This range of models will allow us to investigate different thermodynamic contributions to crystallization transitions.
[1] Valeria Molinero and Emily B. Moore. Water modeled as an intermediate element between carbon and silicon. The Journal of Physical Chemistry B, 113(13):4008–4016, 2009.
* Anni Määttänen1 A. Määttänen1, J. M. C. Plane2
1 LATMOS/IPSL, Université Versailles Saint-Quentin-en-Yvelines, Sorbonne université, CNRS, Guyancourt, France 2School of Chemistry, University of Leeds, Leeds, UK
Title: "Heterogeneous ice nucleation on Mars: formation of mesospheric clouds"
Abstract: Heterogeneous ice nucleation is the main and probably singular pathway for cloud formation in the Martian atmosphere (95% CO2, <<1% of H2O) that hosts an ample amount of mineral dust, lofted from the surface by dust devils and dust storms. On Mars, both water vapour and CO2 condense as ice, at varying altitudes from near the surface to up to 100 km. The mesospheric clouds (>40 km) have been observed to be formed mainly of CO2 ice crystals (Montmessin et al. 2007, Määttänen et al. 2010, Aoki et al. 2018). Some of the outstanding questions in the community during the last decade have been concerning the formation of the mesospheric clouds. We have been able to explain their spatial and temporal distribution through an interplay between atmospheric tides and gravity waves (Gonzalez- Galindo et al. 2011, Spiga et al. 2012). A mystery remains around the Ice Nuclei (IN) present in the very rarefied mesospheric atmosphere (pressure ~1 µbar), and it has been shown that, in addition to the mineral dust lifted from the planet’s surface, an exogenous supply of IN is required (Listowski et al. 2014). Recent observations by the IUVS (Imaging Ultraviolet Spectrograph) instrument on the MAVEN (Mars Atmosphere and Volatile EvolutioN) satellite have revealed a persistent layer of Mg+ atoms around 90 km without a corresponding layer of neutral Mg above the instrumental detection limit, and in contrast to expectations based on the terrestrial Mg/Mg+ layers. The non-detection of Mg was explained by Plane et al. (2018) through the formation of MgCO3. Since such metal carbonates have very large dipole moments, they are readily hydrated up to MgCO3(H2O)6. These clusters can coagulate to form “dirty ice” particles that have properties favourable for nucleation of CO2 (contact parameter close to that of CO2 on water ice, 0.952, Glandorf et al. 2002) and formation of mesospheric clouds. In this poster, we will present an overview of the Martian mesospheric clouds and focus particularly on their formation and the potential IN candidates.
- Aoki, S., Y. Sato, M. Giuranna, P. Wolkenberg, T.M. Sato, H. Nakagawa, Y. Kasaba (2018), Mesospheric CO2 ice clouds on Mars observed by Planetary Fourier Spectrometer onboard Mars Express, Icarus 302, pp. 175-190, https://doi.org/10.1016/j.icarus.2017.10.047. - Glandorf, D.L., Anthony Colaprete, Margaret A. Tolbert, Owen B. Toon (2002), CO2 Snow on Mars and Early Earth: Experimental Constraints, Icarus 160, pp. 66-72, https://doi.org/10.1006/icar.2002.6953. - González-Galindo, F., A. Määttänen, F. Forget, A. Spiga (2011), The Martian mesosphere as revealed by CO2 cloud observations and General Circulation Modeling, Icarus 216, 10- 22, doi:10.1016/j.icarus.2011.08.006
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- Listowski, C., A. Määttänen, F. Montmessin, A. Spiga, F. Lefèvre, Modeling the microphysics of CO2 ice clouds within wave-induced cold pockets in the Martian mesosphere (2014), Icarus 237, 239-261, doi: 10.1016/j.icarus.2014.04.022. - Määttänen, A., F. Montmessin, B. Gondet, F. Scholten, H. Hoffmann, E. Hauber, F. González-Galindo, A. Spiga, F. Forget, G. Neukum, J.-P. Bibring, J.-L. Bertaux (2010), Mapping the mesospheric CO2 clouds on Mars: MEx/OMEGA and MEx/HRSC observations and challenges for atmospheric models. Icarus, 209, 2, 452–469, 2010. - Montmessin, F., B. Gondet, J.-P. Bibring, Y. Langevin, P. Drossart, F. Forget, and T. Fouchet (2007), Hyperspectral imaging of convective CO2 ice clouds in the equatorial mesosphere of Mars, J. Geophys. Res., 112, E11S90, doi: 10.1029/2007JE002944. - Plane, J. M. C., Carrillo-Sanchez, J. D., Mangan, T. P., Crismani, M. M. J., Schneider, N. M. and A. Määttänen (2018), Meteoric Metal Chemistry in the Martian Atmosphere. Journal of Geophysical Research: Planets, 123, 695–707. https://doi.org/10.1002/2017JE005510 - Spiga, A., F. González-Galindo, M.-Á. López-Valverde, and F. Forget (2012), Gravity waves, cold pockets and CO2 clouds in the Martian mesosphere, Geophys. Res. Lett., 39, L02201, doi: 10.1029/2011GL050343.
* Deepak Ojha Deepak Ojha and Thomas D. Khüne Department of Chemistry, Paderborn University
Title: "On Hydrogen Bond Strength and Vibrational Spectroscopy of Liquid Water"
Abstract: In the present work, we introduce two new metrics i.e hydrogen bond strength and charge transfer between the donor/acceptor water molecules as a measure of hydrogen bond rearrangement dynamics. Further, we also employ a simple model based on energy flux through the donor-acceptor water pair to quantify the extent of local hydrogen bond network reorganization. Thereby we report a linear relationship between the OH stretch frequency and the charge/energy transfer through donor-acceptor water pair. We demonstrate that the fluctuations in hydrogen bond strength and charge transfer can be used as an analog of vibrational frequency fluctuations for determining the third-order non-linear spectroscopic observables like the short-time slope of three pulse photon echo (S3PE). The timescales obtained from hydrogen bond strength correlation and charge transfer correlation decay are in excellent agreement with frequency-time correlation function calculated theoretically and also with recent vibrational echo experiments.
* Olli H. Pakarinen O. H. Pakarinen1, C. Pulido Lamas1, and H. Vehkamäki1 1INAR/Physics, University of Helsinki, Finland.
Title: "Ice nucleation in confined geometry and the role of latent heat"
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Abstract: Understanding the way in which ice forms is of great importance to many fields of science. Pure water droplets in the atmosphere can remain in the liquid phase to nearly -40º C. Crystallization of ice in the atmosphere therefore typically occurs in the presence of ice nucleating particles (INPs), such as mineral dust or organic particles, which trigger heterogeneous ice nucleation at clearly higher temperatures.
Experiments have shown in great detail what is the IN activity of different types of compounds, and recently also clarified the importance of small surface features such as surface defects. The molecular-scale Figure 1: Experimentally realizable processes responsible for ice nucleation are still not etched Si (001) pits increase ice well known, however. In recent years, several nucleation activity due to geometric computational studies have advanced our confinement. understanding of the details of ice nucleation in many materials, and also the role of defects. Recently simulations showed enhanced ice nucleation efficiency in confined geometry such as wedges or pits (Bi, Cao and Li, 2017).
We are studying these topics by utilizing the monatomic water model (Molinero and Moore, 2009) for unbiased molecular dynamics (MD) simulations, where a system including a defected surface, such as pyramidal pits, steps or surface cracks, immersed in water, is cooled continuously below the melting point over tens of nanoseconds of simulation time and crystallization is followed.
Results of simulations on pyramidal pits on Si (100) surfaces (Fig. 1), an experimentally realizable system, show a clear (ΔT > 10º C) enhancement of ice nucleation compared to flat Si (100) or Si (111) surfaces, in agreement with initial experimental findings of preference of ice to nucleate at these sites. Understanding the enhanced activity in such confined geometry may lead to characterization of active sites on some ice nucleating materials.
With a combination of finite difference calculations and molecular dynamics simulations we also show that the release of latent heat from ice growth has a noticeable effect on both the ice growth rate and the initial structure of the forming ice. However, latent heat is found not to be as critically important in controlling immersion nucleation as it is in vapor-to-liquid nucleation [Tanaka et al. 2017].
This work was supported by the Academy of Finland Center of Excellence programme (grant no. 307331) and ARKTIKO project 285067 ICINA, by ERC Grant 692891-DAMOCLES and by supercomputing resources at CSC - IT Center for Science Ltd.
- Bi, Y., B. Cao and T. Li (2017). Nat. Commun. 8, 15372. - Molinero, V. and E. B. Moore (2009). J. Phys. Chem. B 113, 4008. - Tanaka, K. K et al. (2017). Phys. Rev. E 96, 022804.
* Soroush Rasti Soroush Rasti and Jörg Meyer Theoretical Chemistry, Leiden Institute of Chemistry, Leiden University, The Netherlands
Title: "A comparison of empirical force fields and density functional theory for modeling ice"
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Abstract: Atomistic modeling of complex dynamical processes and extensive statistical sampling usually of concomitant coarse-grained parameter commonly relies on established force fields for H2O [1,2]. These force fields are parameterized to data from experiments or first-principles calculations – if the latter are sufficiently accurate. In particular, despite 30 years of computer simulations of water, an accurate description of the phase diagram based on atomistic chemical interaction models is still challenged by accurately accounting for hydrogen bonding and van-der-Waals interactions [3,4].
In this work, we compile a systematic comparison between many common force fields and density functional theory, including the recently developed SCAN functional that has shown very promising performance for ice structures [5]. For all proton-ordered crystalline phases of ice we calculate the full phonon dispersions and concomitant density of states in order to include them in the thermodynamic properties within the quasi-harmonic approximation [6]. We analyze the hydrogen bonding and equilibrium volumes as well as phase transition pressures. Furthermore, focusing on the (0001) surface of ice Ih, we likewise compare surface energies and will present first results for surface vibrational properties.
[1] G. C. Sosso et al., Chem. Rev. 116, 7078 (2016). [2] B. Weber et al., J. Phys. Chem. Lett. 9, 2838 (2018). [3] E. Sanz et al., Phys. Rev. Lett. 92, 255701 (2004). [4] B. Santra et al., Phys. Rev. Lett. 107, 185701 (2011). [5] J. Sun et al., Nat. Chem. 8, 831 (2016). [6] R. Ramírez et al., J. Chem. Phys. 137, 044502 (2012).
* Bernard Reischl Golnaz Roudsari, Bernhard Reischl, Olli H. Pakarinen and Hanna Vehkamäki Institute for Atmospheric and Earth Science Research / Physics, Faculty of Science, University of Helsinki, Finland.
Title: "Effect of Defects on Heterogeneous Ice Nucleation at Silver Iodide Surfaces"
Abstract: Silver iodide (AgI) is an excellent ice-nucleating agent, which is widely used in cloud seeding [1]. The ice-nucleating efficacy of crystals is related to their specific crystallographic features. However, our knowledge of the microscopic mechanisms responsible for the ice- forming properties of different materials is relatively limited. Previous theoretical work has
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shown that ice nucleation on AgI occurs on time scales accessible to unbiased molecular dynamics simulations [2], unlike in many other systems relevant for heterogeneous ice nucleation in the atmosphere, which makes this material a good benchmark system.
In this study, we investigate the ability of non-ideal AgI surfaces to nucleate and grow ice, using molecular dynamics simulations with the TIP4P/ice model of water [3] and AgI/water interactions proposed by Hale and Kiefer [4]. We present simulations on AgI surfaces exhibiting point defects, step edges, or kink sites, and compare them to simulations of the corresponding ideal, flat β-AgI surfaces. This study will help identify which surface features can act as efficient ice-nucleating sites, and consequently we may even be able to suggest designs of new artificial materials optimized for cloud seeding applications.
This work was supported by the Academy of Finland Center of Excellence programme (grant no. 307331) and ARKTIKO project 285067 ICINA, the National Center for Meteorology and Seismology, Abu Dhabi, UAE, under the UAE Research Program for Rain Enhancement Science, as well as ERC Grant 692891-DAMOCLES. Supercomputing resources were provided by CSC–IT Center for Science, Ltd, Finland.
[1] H. R. Pruppacher and J. D. Klett, Microphysics of Clouds and Precipitation, Springer, New York (2010). [2] S. A. Zielke, A. K. Bertram and G. N. Patey, J. Phys. Chem. B 119, 9049 (2014). [3] J. L. F. Abascal, E. Sanz, R. García Fernández and C. Vega, J. Chem. Phys. 122, 234511 (2005). [4] B. N. Hale and J. Kiefer, J. Chem. Phys. 73, 923 (1980).
* J. Marcos Salazar Antoine Patt1, Jean-Marc Simon2, Sylvain Picaud1 and J. Marcos Salazar2 1 Institut UTINAM UMR 6213, CNRS Université de Bourgogne Franche-Comté, F-25000 Besançon, France 2 Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303CNRS Université de Bourgogne Franche-Comté, F-21078 Dijon Cedex, France
Title: "A Grand Canonical Monte Carlo Study of the N2, CO and Mixed N2-CO Clathrate Hydrates"
Abstract: In this paper we report Grand Canonical Monte Carlo simulations to characterize the competitive trapping of CO and N2 molecules into clathrates, for various gas compositions in the temperature range from 50 to 150 K. The simulations evidence a preferential trapping of CO with respect to N2. This leads to the formation of clathrates that are preferentially lled with CO at equilibrium. This is irrespective of the composition of the gas phase, the fugacity and the temperature. Moreover, the results of the simulations show that the small cages of the clathrate structure are always lled in rst place, and this is independent of either the guest structure or the temperature. This issue has been associated to the rather signi cant di er- ences in the calculated heats of encapsulation (∼2-3 kJ/mol) between the small and the larges cages. In addition, calculations with the simpli ed ideal adsorbed solution theory (IAST) are developed for allowing a comparison with the results arising from the GCMC simulations. Interestingly, this shows that the occupancy isotherms of the mixed N2-CO clathrates can be perfectly represented by knowing the occupancy isotherms of the corresponding single- guest clathrates. This suggests that experiments performed with the single guest CO and N2 clathrates might be su cient to get information concerning the corresponding mixed clathrates by using the IAST approach.
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* Sapna Sarupria Brittany Glatz1, Jiarun Zhou1, Nurun Nahar Lata2, Sapna Sarupria, Will Cantrell2 1Chemical and Biomolecular Engineering, Clemson University 2Department of Physics, Michigan Technological University (MTU)
Title: "Bridging experiments and molecular simulations to elucidate heterogeneous ice nucleation"
Abstract: Heterogeneous ice nucleation is the primary pathway for ice formation in the atmosphere. Different types of particles such as pollen, bacteria, and mineral dusts influence ice nucleation. In some cases, these particles allow ice to form at temperatures as high as - 3oC. In comparison, homogeneous ice nucleation (i.e. nucleation in the absence of any foreign particle) occurs at -40oC. Even though it is appreciated that particles can enhance ice nucleation, the understanding of the interplay between the surface’s chemistry and physical properties and its ability to nucleate ice is lacking. There is no framework to predict the ice nucleating ability of a surface based on its characteristics. The primary challenge to this end is the ability to access the relevant length and time scales in both experiments and simulations. Nucleation occurs in nano-to-micro second timescales and lengthscales of few hundred-to-thousand molecules. These are difficult to probe in experimental studies. In principle, these are ideal scales for molecular simulations, however, the challenge comes from the fact that ice nucleation is a rare event – i.e., an event which occurs at frequencies lower than the simulation sampling time. In our research, using advanced sampling techniques combined with molecular dynamics (MD) simulations we evaluated the role of various surface properties on ice nucleation. We have studied three types of surfaces – kaolinite- based, silver iodide-like and mica surfaces. Capitalizing on the power of molecular simulations we have carefully probed the effects of specific surface properties such as hydrogen bonding abilities, lattice spacing, and surface charge distribution on the propensity to observe ice nucleation. Furthermore, we related the structure of the metastable liquid near the surface to the propensity of ice nucleation [1,2]. We find that certain characteristics of the liquid water structure – related to the orientations of water molecules near the surface – are good indicators of possible ice nucleation.[1,2] We are expanding our understanding to correlate these observations with experimental findings. To this end, we focus on studies of ice nucleation near mica surfaces. Mica surfaces can be cleaved to be atomistically smooth in experiments. This makes them an ideal choice for a collaborative experimental and simulation investigation since in simulations the surfaces are usually made atomically smooth. We study the effects of surface ion and charge distribution along with the effects of lattice spacing on ice nucleation. Our simulations indicate that the interfacial structure of water near the mica surfaces provides signature characteristics to predict the ice nucleating propensity. In experiments, we have used Fourier Transform Infrared Spectroscopy to study the liquid water structure near the mica surfaces.[3,4] While we do not probe the ice forming cluster, we can measure the liquid water structure and the temperature of ice nucleation. Through this combined approach, we evaluate the role of surface chemistry on ice nucleation. This combined approach provides information regarding the molecular mechanisms of ice nucleation near mica surfaces and the effect of surface ions on this behavior. In this poster, we will present these results and discuss how we bridge experimental and simulations findings.
[1] Glatz, Brittany and Sarupria, S., “Heterogeneous ice nucleation: Interplay of surface properties and their impact on water orientations”, (Langmuir, Just Accepted Manuscript, 2017) [DOI: 10.1021/acs.langmuir.7b02859, 2017] [2] Glatz, B. and Sarupria, S, “The surface charge distribution affects the ice nucleating efficiency of silver iodide”, Journal of Chemical Physics 145, 211924, 2016
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[3] Niehaus, J., K. W. Bunker, S. China, A. Kostinski, C. Mazzoleni, and W. Cantrell. “A technique to measure ice nuclei in the contact mode.” J. Atmos. Oceanic Technol., 31, 913– 922, 2014 [4] Cantrell, W. and G. Ewing. “Attenuated (but not Total) Internal Reflection FTIR spectroscopy of thin films”. Applied Spectroscopy, 56, 665-669, 2002.
* Donguk Suh Naoya Shimazu1, Daisuke Takaiwa1, Donguk Suh2, Kenji Yasuoka1 1Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan 2Department of Mechanical Engineering, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
Title: "Surfactant Molecules for Ice Crystal Growth Inhibition by Molecular Dynamics"
Abstract: Molecular dynamics was used to simulate heterogeneous ice nucleation of a water/CTAB/ice system. A CTAB molecule was chosen as the inhibitor because it is amphiphilic like many antifreeze proteins. The ice growth rate of a pure system was compared for the basal [0001], first prism [10-10], and secondary prism plane [11-20], where the secondary prism was the fastest followed by the first prism plane. When CTAB was added to the ice-liquid water system, ice growth was clearly impeded. Even when ice starts growing away from the CTAB molecule, the hydrophilic head would eventually get caught in the water/ice interface. Once the head of the CTAB was encapsulated in the advancing water/ice interface, the alkyl chain would constantly move around and obstruct hydrogen bonds from forming networks that are essential for the ice crystal to grow. When the interface clears the length of the body of the CTAB molecule, ice crystallization resumes at its original rate. In short, the inhibition of ice growth is a combination of the hydrophilic head acting as an anchor and the dynamic motion of the hydrophobic tail hindering stable hydrogen bonding for ice growth.
* Erik S. Thomson Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden
Title: "Water interactions with organic surfaces: uptake, accommodation, and ice nucleation"
Abstract: Organic surfactants play a large role in the atmosphere due to their ubiquity and diversity. Such surfactants have been shown to enhance and/or suppress the adsorption and desorption kinetics of atmospheric particles [e.g., 1,2], and thus can promote and/or hinder water uptake, potentially changing the hydrophilicity of atmospheric nanoparticles. Even molecules dominated by hydrophobic functional groups can exhibit surprising hydrophilic behaviours [3]. As a result of these fundamental molecular processes, alcohol surfactant layers have size and temperature dependent effects on ice nucleation [4] and growth morphology, in addition to molecular water uptake. Herein the results of successive generations of Environmental Molecular Beam experiments that provide molecular-level information on water interactions with organic surfaces are summarized. Water collisions with organic surfaces and the resulting fate of water molecules are examined to illuminate fundamental processes of accommodation and bulk liquid/ice nucleation. The potential effects on cloud evolution and lifetime and thereby impacts on fundamental environmental processes like the water cycle and radiative balance are discussed.
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Classical vs Non-Classical Nucleation of Methane Hydrate
Arjun Wadhawan1 and Peter G Bolhuis 1
1Van’t Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands. е-mail: [email protected]
Nucleation is a complex phenomenon in which various degrees of freedom play a role for the phase transformation to occur. This preliminary step towards crystal growth still poses unsolved questions. Molecular simulation is able to elucidate the nucleation phenomenon in atomistic details, often inaccessible in experiments due to spatial and/or temporal resolution. Recent simulation studies showed that Classical Nucleation Theory (CNT) may not be sufficient to describe nucleation and that there may be a non-classical component involved. In this study, we use unbiased simulation (700 μs) of fully atomistic models of methane/water mixtures and show how methane hydrates nucleate at experimental temperatures(T). Methane[1] Thomson, hydrate E.S. et (MH) al. JPCL, is 2(17):2174 a nonstoichiometric–2178, 2011. solid compound composed of water cages [2] Kong, X. et al. JPCC, 116(16):8964–8974, 2012. 1 (like ice) with[3] Johansson,methane S. molecules et al. PCCP, in trapped preparation. inside . Understanding it’s formation is of importance to [4] Thomson, E. S. et al. ACP, 15, 1621-1632, 2015. both oil industry and environmentalists. At low undercooling the formation of an initial nucleus is a 2 extremely rare* Arjun event Wadhawan in computer simulation. In the past, researchers have circumvented the rare event problemArjun by Wadhawan biasing1 and the Peter simulation G Bolhuis1 or by forcing the process at high undercooling. Both these 1Van’t Hoff Institute for Molecular Sciences techniques Universiteitlead to avan solid Amsterdam, phase Science but Parknot 904,in the1098 mostXH Amsterdam, stable The hydrate Netherlands. form. Henceforth there have е-mail: [email protected] been speculations whether or not the nucleation of MH is non-classical in nature. Title: "Classical vs Non-Classical Nucleation of Methane3 Hydrate" Here, we use Transition Path Sampling to generate reactive trajectories connecting liquid and solid states.Abstract: This A new allows Nucleation deciphering is a complex phenomenon the true inmechanism, which various degrees size ooff freedom the critical nucleus and the play a role for the phase transformation to occur. This preliminary step towards crystal growth properties ofstill the poses free unsolved energy questions. barrier Molecular involved simulation in is the able process. to elucidate We the nucleation find that within the relevant phenomenon in atomistic details, often inaccessible in experiments due to spatial and/or temperaturetemporal range resolution. there exist Recent two simulation mechanistic studies showed nucleation that Classical routes, Nucleation one reaching Theory a crystal, the other (CNT) may not be sufficient to describe nucleation and that there may be a non-classical forming an component amorphous involved. solid. In this At study, low we T, use nucleation unbiased simulation of the (700 amorphous μs) of fully atomistic phase is sampled, and the models of methane/water mixtures and show how methane hydrates(12) nucleate at experimental process is temperatures(T). dominated by kinetics (high number of 5 cage) which suggests non-classical pathways. AtMethane higher hydrate T, thermodynamics(MH) is a nonstoichiometric dominates solid compound and composed a crystalline of water cages phase (like persists (high number ice) with methane molecules trapped inside [1]. Understanding it’s formation is of importance (12) (2) of 5 6 ) indicatingto both oil industry that the and environmentalists.mechanism is At very low undercoolingmuch in line the formationwith CNT. of an At initial intermediate T, both the nucleus is a extremely rare event in computer simulation. In the past, researchers [2] have crystalline andcircumvented amorphous the rare hydrates event problem can by biasingform withthe simulation almost or equal by forcing probabilities. the process at Our results shed light high undercooling. Both these techniques lead to a solid phase but not in the most stable upon the longhydrate-standing form. Henceforth discussion there have of MHbeen nucleationspeculations whether and showsor not the thisnucleation switching of MH behaviors is non-classical in nature.
[1] E. D. Sloan,Here, C. A.we Koh,use Transition Clathrate Path Hydrates Sampling of [3] Natural to generate Gases reactive (CRC trajectories Press, connectingBoca Raton, liquid FL, 2008) and solid states. This allows deciphering the true mechanism, size of the critical nucleus and [2] Walsh MR,the Koh properties CA, Sloan of the ED, free Sum energy AK, barrier Wu DT involved Science, in the (2009 process.) 326(5956):1095 We find that within–1098. the [3] P. G. Bolhuis,relevant D. Chandler, temperature C. range Dellago, there andexist P. two L. mechanistic Geissler, Annu.nucleation Rev. routes, Phys. one Chem. reaching (2002 a ), 53, 91 crystal, the other forming an amorphous solid. At low T, nucleation of the amorphous phase is sampled, and the process is dominated by kinetics (high number of 5(12) cage) which suggests non-classical pathways. At higher T, thermodynamics dominates and a crystalline phase persists (high number of 5(12)6(2)) indicating that the mechanism is very much in line with CNT. At intermediate T, both the crystalline and amorphous hydrates can form with almost equal probabilities. Our results shed light upon the long-standing discussion of MH nucleation and shows this switching behaviors
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[1] E. D. Sloan, C. A. Koh, Clathrate Hydrates of Natural Gases (CRC Press, Boca Raton, FL, 2008) [2] Walsh MR, Koh CA, Sloan ED, Sum AK, Wu DT Science, (2009) 326(5956):1095–1098. [3] P. G. Bolhuis, D. Chandler, C. Dellago, and P. L. Geissler, Annu. Rev. Phys. Chem. (2002), 53, 91
* Thomas Whale Thomas F. Whale1 and Gabriele C. Sosso2 1 School of Earth and Environment, University of Leeds, UK 2 Department of Chemistry, University of Warwick, UK
Title: "Unclogging the block: Combined experimental and computational studies of ice nucleation on cholesterol surfaces"
Abstract: Direct experimental examination of heterogeneous ice nucleation remains extremely challenging due to the small spatial and temporal extent of the ice critical nucleus, and its uncertain location in any ice nucleation process. As a result, the vast back-catalogue of ice nucleation experiments in the literature has revealed little conclusive regarding why some substances nucleate ice better than others. Various molecular dynamics techniques are capable of directly investigating the nucleation of ice on heterogeneous substrates but necessarily simulate unrealistically short timescales and oversimplified surface structures. This poster discusses possible routes to combining the strengths of experimental and computational techniques for investigating heterogeneous ice nucleation in order to mitigate their relative weaknesses and improve overall understanding of this vital process. The example of recent combined work on cholesterol is used an example.
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