DOCSLIB.ORG

Data-Driven Learning and Prediction of Inorganic Crystal Structures

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Data-Driven Learning and Prediction of Inorganic Crystal Structures Faraday Discussions Cite this: Faraday Discuss.,2018,211,45 View Article Online PAPER View Journal | View Issue Data-driven learning and prediction of inorganic crystal structures ab cd a Volker L. Deringer, * Davide M. Proserpio, Gabor´ Csanyi´ and Chris J. Pickardef Received 16th February 2018, Accepted 6th March 2018 DOI: 10.1039/c8fd00034d Crystal structure prediction algorithms, including ab initio random structure searching (AIRSS), are intrinsically limited by the huge computational cost of the underlying quantum-mechanical methods. We have recently shown that a novel class of machine Creative Commons Attribution 3.0 Unported Licence. learning (ML) based interatomic potentials can provide a way out: by performing a high- dimensional fit to the ab initio energy landscape, these potentials reach comparable accuracy but are orders of magnitude faster. In this paper, we develop our approach, dubbed Gaussian approximation potential-based random structure searching (GAP- RSS), towards a more general tool for exploring configuration spaces and predicting structures. We present a GAP-RSS interatomic potential model for elemental phosphorus, which identifies and correctly “learns” the orthorhombic black phosphorus (A17) structure without prior knowledge of any crystalline allotropes. Using the tubular structure of fibrous phosphorus as an example, we then discuss the limits of free This article is licensed under a searching, and discuss a possible way forward that combines a recently proposed fragment analysis with GAP-RSS. Examples of possible tubular (1D) and extended (3D) hypothetical allotropes of phosphorus as found by GAP-RSS are discussed. We believe Open Access Article. Published on 12 April 2018. Downloaded 9/28/2021 2:16:12 AM. that in the future, ML potentials could become versatile and routine computational tools for materials discovery and design. Introduction Exploring and cataloguing new crystal structures is one of the principal tasks in chemistry. Decades of careful experimental work are collected in the Inorganic Crystal Structure Database (ICSD)1 and the Cambridge Structural Database (CSD),2 which have been impressive examples of “big data” since long before the aDepartment of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK. E-mail: [email protected] bDepartment of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK cDipartimento di Chimica, Universita` degli Studi di Milano, Milano, Italy dSamara Center for Theoretical Materials Science (SCTMS), Samara State Technical University, Samara 443100, Russia eDepartment of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK fAdvanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai, 980-8577, Japan This journal is © The Royal Society of Chemistry 2018 Faraday Discuss.,2018,211,45–59 | 45 View Article Online Faraday Discussions Paper phrase became fashionable. While structural space has traditionally been explored by synthesis, more recent work has shown that ab initio structure searching can play an important and complementary role in this regard. Computational tools, including genetic algorithms,3–5 particle swarm optimisa- tion,6,7 or ab initio random structure searching (AIRSS),8,9 can predict structures that are (sometimes) far from what chemical intuition would suggest. Many of these predictions have subsequently been validated by experiments10–14 or have given rise to databases of their own.15 We only mention in passing the prediction of organic molecular crystal structures, which has likewise seen fundamental breakthroughs.16–19 Despite their predictive power, these structure searching methods are nor- mally driven by quantum-mechanical density-functional theory (DFT) computa- tions, and therefore they are limited to systems with relatively small unit cells. The allotropes of elemental phosphorus,20–22 which are the topic of the present paper, directly illustrate the problem at hand. The thermodynamically stable “black” (orthorhombic) form, as well as the high-pressure As-type (rhombohedral) allotrope, exhibit simple crystal structures with only one symmetry-independent atom each (Table 1). Such systems are easily amenable to ab initio crystal struc- ture prediction, and various, especially layered, hypothetical allotropes have been 23–32 33 Creative Commons Attribution 3.0 Unported Licence. proposed in recent years. On the other hand, “violet” (Hittorf’s) phosphorus has a notoriously complex structure that was solved more than 100 years aer the initial synthesis34 and contains no fewer than 21 symmetry-independent atoms in the unit cell. Systems of this size have hitherto been out of reach for ab initio crystal structure prediction. It has recently been suggested that machine learning (ML) based interatomic potentials could help with this long-standing issue.35–38 Such potentials are tted to reference databases of DFT energies and forces and, once generated, they allow one to perform atomistic simulations with close to DFT quality but at a compu- This article is licensed under a tational cost that is orders of magnitude lower.39 Indeed, we have recently shown Open Access Article. Published on 12 April 2018. Downloaded 9/28/2021 2:16:12 AM. Table 1 Experimentally known crystal structures of phosphorus.20 Z is the number of atoms in the conventional unit cell; Z0 gives the number of symmetry-inequivalent atoms in the cell, and is therefore a measure of structural complexity. The molecular (“white”) and amorphous (“red”) forms are omitted from this study for simplicityb Space group ZZ0 Source Ref. Black P Cmca 8 1 High-pressure synthesis 43 As-type Pa R3m 2 1 From black P (p > 5 GPa) 44 Simple cubic P Pm3m 1 1 From black P (p > 11 GPa) 44 Hittorf’sP P2/c 84 21 Slow cooling from Pb melt 34 Fibrous P P1 42 21 Resublimation with I catalyst 45 a Occasionally referred to as “blue P” in recent literature,46 especially in the monolayer form. b To explore whether our GAP would be able to nd molecular (“white”) P, we carried out À a set of preliminary searches at low density (1.0 g cm 3). The resulting structures did include distorted P4 units, but also other small fragments, and we expect that the GAP will need to have “seen” these in iterative training to distinguish them more clearly. We also expect that fully capturing the intricate structural details of white P, including its packing variants,74 will require additional reference data; this is the topic of ongoing work. Regarding amorphous forms, our searches are restricted to relatively small periodic unit cells which cannot fully represent the amorphous allotrope(s). 46 | Faraday Discuss.,2018,211,45–59 This journal is © The Royal Society of Chemistry 2018 View Article Online Paper Faraday Discussions that an ML-based Gaussian approximation potential (GAP), initially developed for amorphous carbon,40 can be used to identify crystalline allotropes.36 This has added around 150 entries to the Samara Carbon Allotrope Database (SACADA, ref. 15). Very recently, the use of ML to speed up global searching and crystal structure optimization itself has been reported,41,42 but we focus here on the use of explicit interatomic potentials (“force elds”) for this purpose. What is more, in recent work,37 we have argued that RSS can be used to construct the interatomic potential from scratch, exploring and tting a complex potential energy surface (PES) at the same time. This points towards a more general “data-driven” strategy for atomistic materials modelling. In this Discussion paper, we aim to take new steps in this direction and further develop our emerging method (which we call “GAP-RSS”). Aer briey summa- rising its components, we present results for elemental phosphorus, generating and applying the rst GAP-RSS potential for this material. Our protocol “discovers” the crystal structure of black P during the iterations and, by construction, adds it to the reference database without prior knowledge of any existing allotropes. We then use this potential for some exercises in crystal structure prediction: we show that a brous allotrope of P (Table 1) appears to be prohibitively hard to nd in free searches, and we outline the use of an alternative Creative Commons Attribution 3.0 Unported Licence. approach, showing exemplary predicted structures in 1D and 3D. We also discuss open questions and expected future directions. Methodology The protocol for GAP-RSS potential tting and structure searching consists of three components: single-point DFT computations, GAP tting to an updated reference database, and structural optimisation using GAP. We give details of these in sequence, and an overview is provided in Fig. 1. This article is licensed under a DFT computations These provide the input data for GAP tting: initially, single-point DFT compu- Open Access Article. Published on 12 April 2018. Downloaded 9/28/2021 2:16:12 AM. tations are done for randomised atomic congurations, later, for intermediates or local minima of GAP-RSS searches. We obtain these data using standard DFT procedures, with high numerical accuracy to minimise noise in the input for tting. In this work, we used the PBEsol functional,47 which has been validated for black P before,48 and on-the-y ultra-so pseudopotentials as implemented in CASTEP.49 Reciprocal space was sampled on dense k-point meshes (maximum À spacing 0.02 A˚ 1). The cut-off energy for plane-wave expansions was 600 eV, and an extrapolation scheme was used to counteract nite-basis errors.50 In Fig. 1, all parts that involve single-point DFT computations (viz. the construction of the reference database) are enclosed by dashed lines. GAP tting With reference data available, an interatomic potential is tted to these using GAP. The framework was introduced in 2010 (ref. 51) and has since been used to generate potentials for diverse molecular and solid-state materials.40,52–54 Ahigh-dimensional t to reference energy and force data is performed based on structural similarity or kernel functions, comparing atomic environments one by one.
Load more

Recommended publications
  • Black Phosphorus As a New Lubricant
    Friction 6(1): 116–142 (2018) ISSN 2223-7690 https://doi.org/10.1007/s40544-018-0204-z CN 10-1237/TH RESEARCH ARTICLE Black phosphorus as a new lubricant Wei WANG, Guoxin XIE*, Jianbin LUO* State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China Received: 20 June 2017 / Revised: 18 October 2017 / Accepted: 07 December 2017 © The author(s) 2018. This article is published with open access at Springerlink.com Abstract: In recent years, a new 2D-layered material—black phosphorus (BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic structure. With the development of the synthesis and modification methods of BP, its extensive applications, e.g., transistors, batteries and optoelectronics have emerged. In order to explore its full potential, research into the tribological properties of BP 2D-layered materials such as lubrication additives and fillers in self-lubricating composite materials would be not only of high scientific value but also of practical significance. In this work, recent advances on the friction and lubrication properties of BP nanosheets made by our group, including the micro-friction properties, the lubrication properties of BP nanosheets as water-based and oil-based lubrication additives, and the friction and wear of BP/PVDF composites will be presented. Finally, the future challenges and opportunities in the use of BP materials as lubricants will be discussed. Keywords: black phosphorus; two-dimensional (2D) material; lubricant additive; self-lubricating composite materials; friction 1 Introduction certain period owing to the finite lubricant thickness, and it can be easily affected by the environment.
    [Show full text]
  • Download (4Mb)
    Original citation: Zhenqing, Li, He, Chaoyu, Ouyang, Tao, Zhang, Chunxiao, Tang, Chao, Roemer, Rudolf A. and Zhong, Jianxin (2018) New allotropes of phosphorene with remarkable stability and intrinsic piezoelectricity. Physical Review Applied, 9 . 044032. doi:10.1103/PhysRevApplied.9.044032 Permanent WRAP URL: http://wrap.warwick.ac.uk/101768 Copyright and reuse: The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available. Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher statement: © 2018 American Physical Society Published version: https://doi.org/10.1103/PhysRevApplied.9.044032 A note on versions: The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher’s version. Please see the ‘permanent WRAP url’ above for details on accessing the published version and note that access may require a subscription. For more information, please contact the WRAP Team at: [email protected] warwick.ac.uk/lib-publications New allotropes of phosphorene with remarkable stability and intrinsic piezoelectricity Zhenqing Li,1, 2 Chaoyu He,1, 2, ∗ Tao Ouyang,1, 2 Chunxiao Zhang,1, 2 Chao Tang,1, 2, y Rudolf A.
    [Show full text]
  • Recent Advances in Synthesis, Properties, and Applications of Phosphorene
    www.nature.com/npj2dmaterials REVIEW ARTICLE OPEN Recent advances in synthesis, properties, and applications of phosphorene Meysam Akhtar1,2, George Anderson1, Rong Zhao1, Adel Alruqi1, Joanna E. Mroczkowska3, Gamini Sumanasekera1,2 and Jacek B. Jasinski2 Since its first fabrication by exfoliation in 2014, phosphorene has been the focus of rapidly expanding research activities. The number of phosphorene publications has been increasing at a rate exceeding that of other two-dimensional materials. This tremendous level of excitement arises from the unique properties of phosphorene, including its puckered layer structure. With its widely tunable band gap, strong in-plane anisotropy, and high carrier mobility, phosphorene is at the center of numerous fundamental studies and applications spanning from electronic, optoelectronic, and spintronic devices to sensors, actuators, and thermoelectrics to energy conversion, and storage devices. Here, we review the most significant recent studies in the field of phosphorene research and technology. Our focus is on the synthesis and layer number determination, anisotropic properties, tuning of the band gap and related properties, strain engineering, and applications in electronics, thermoelectrics, and energy storage. The current needs and likely future research directions for phosphorene are also discussed. npj 2D Materials and Applications (2017) 1:5 ; doi:10.1038/s41699-017-0007-5 INTRODUCTION properties, including high carrier mobility, ultrahigh surface area, Since the discovery of graphene in 2004 (ref. 1), there has been a excellent thermal conductivity, and quantum confinement effect 9 quest for new two-dimensional (2D) materials aimed at fully have been well documented. However, the lack of band gap is a exploring new fundamental phenomena stemming from quantum serious limitation for the use of graphene in electronic devices.
    [Show full text]
  • Download SCOPE Newsletter
    With participation of the European Commission: DG GROW and Joint Research Centre Summary of joint European Commission – ESPP webinar th on P4 (phosphorus) Critical Raw Material, 9 July 2020 This ESPP SCOPE Newsletter summarises discussions at the expert webinar jointly organised by ESPP and the European Commission on 9th July, with participation of Contents the leading companies using phosphorus (P4) or its derivatives in Europe, with additional input from the The EU Critical Raw Materials: “Phosphate Rock” and “Phosphorus”........................................................................... 2 independent industry expert Willem Schipper. The content (Fig. i) Overview numbers: from phosphate rock to P4 / P4-derivatives below has been seen by the participants but does not and applications .................................................................................. 3 represent their position, it represents ESPP’s own How is P4 produced? the phosphorus furnace .............. 4 assessment. Photo: P4 furnace ................................................................................ 4 Schematic: P4 manufacture process (simplified) ................................. 4 This webinar aimed to provide expert input to the European Which chemicals critically depend on P4 / P4 derivatives? . 5 Commission’s MSA (Material System Analysis) of the EU dependency on P4 concerns many industry sectors . 5 specific industrial form of “Phosphorus”, P4, as a Critical (Fig. ii) Production via wet-acid or via P4 / P4 derivatives / ‘thermal’ Raw
    [Show full text]
  • Enhancement of Carrier Transport in Black Phosphorus Through Via Contacts Embedded in H-BN
    GrapheneUS Graphene & 2D Materials International Conference and Exhibition February 14-15, 2019 Myeongjin Lee Won Jong Yoo SKKU Advanced Institute of Nano-Technology, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do, 16419, Korea [email protected] Enhancement of carrier transport in black phosphorus through via contacts embedded in h-BN Black phosphorus (BP), one of the allotropes of phosphorus, is a promising candidate for future nano- electronics and nano-photoelectronics. Unlike conventional two dimensional semiconducting materials which show n-type property and high electron mobility, BP shows p-type property and high hole mobility [1]. However, BP faces limitations in application to future electrical devices since BP is easily degraded in air atmosphere, and therefore attempts are made to prevent BP from being oxidized under air ambient. Here, we employed the via contact method [2] for suppressing degradation of BP. The method is to make direct electrical contact by using metal embedded hexagonal boron nitride (hBN) on BP which was not exposed to air. The fabricated devices showed enhanced carrier transport properties because of the suppressed degradation of BP. The devices also showed low contact resistance since ultraclean interface between metal and BP was formed. Furthermore, by applying forces on the contact interface between metal and BP by atomic force microscopy (AFM) probes, the electrical performance of the devices were enhanced, attributed to the better electrical contact formed between metal and BP. References [1] Likai Li, Yijun Yu, Guo Jun Ye, Qingqin Ge, Xuedong Ou, Hua Wu, Donglai Feng, Xian Hui Chen, and Yuanbo Zhang, Black phosphorus field-effect transistors, Nature Nanotechnology, 9, 372-377, 2014.
    [Show full text]
  • One-Dimensional Pnictogen Allotropes Inside Single- Wall Carbon Nanotubes
    One-dimensional pnictogen allotropes inside single- wall carbon nanotubes Martin Hart,1 Ji Chen,2 Angelos Michaelides,3 Andrea Sella,1 Milo S. P. Shaffer4 and Christoph G. Salzmann*1 1 Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom 2 School of Physics, Peking University, Beijing 100871, P. R. China 3 Thomas Young Centre, Department of Physics and Astronomy, and London Centre for Nanotechnology, University College London, Gower Street, London, WC1E 6BT, United Kingdom 4 Department of Chemistry, Imperial College London, Imperial College Road, London, SW7 2AZ, United Kingdom E-mail: [email protected] 1 ABSTRACT The discovery of phosphorene, a single layer of black phosphorus, has kick-started tremendous research efforts investigating the pnictogen nanomaterials. Arsenene and antimonene have now also been identified and these two-dimensional nanomaterials display physical properties superior to graphene for some applications. Recently, single-wall carbon nanotubes (SWCNTs) have been filled with P4 molecules from the melt and As4 molecules from the vapor phase. Inside the confinement of the SWCNTs, polymerization reactions were observed yielding new one- dimensional pnictogen allotropes. Here we show using high-resolution electron microscopy that such nanostructures can also be observed upon filling SWCNTs from the vapor phase using red phosphorus as the source material. Using larger diameter SWCNTs and filling from the vapor phase favors the formation of double-stranded phosphorus zig-zag ladders observed here for the first time. SWCNTs were generally found to fill well with liquid phosphorus. However, substantial decreases in the filling yields were observed for both phosphorus and arsenic filling of narrow SWCNTs using the vapor route.
    [Show full text]
  • Simulated Scanning Tunneling Microscopy Images of Few-Layer-Phosphorus Capped by Hexagonal Boron Nitride and Graphene Monolayers
    Simulated scanning tunneling microscopy images of few-layer-phosphorus capped by hexagonal boron nitride and graphene monolayers Pablo Rivero,1 Cedric M. Horvath1, Zhen Zhu2, Jie Guan2, David Tom´anek2;∗, and Salvador Barraza-Lopez1∗ 1. Department of Physics, University of Arkansas, Fayetteville, AR 72701, USA 2. Physics and Astronomy Department, Michigan State University, East Lansing, MI 48824, USA (Dated: September 19, 2018) Elemental phosphorous is believed to have several stable allotropes that are energetically nearly degenerate, but chemically reactive. These structures may be capped by monolayers of hexagonal boron nitride (h-BN) or graphene to prevent chemical degradation under ambient conditions. We perform ab initio density functional calculations to simulate scanning tunneling microscopy (STM) images of different layered allotropes of phosphorus and study the effect of the capping layers on these images. At scanning energies within its intrinsic conduction gap, protective monolayers of insulating h-BN allow to distinguish between the different structural phases of phosphorus underneath due to the electronic hybridization with orbitals from the upmost phosphorus atoms: h-BN capping monolayers thus provide a promising route to tell few-layer phosphorus allotropes from one another with local probes. PACS numbers: 68.37.Ef, 31.15.A-, 73.90.+f I. INTRODUCTION tuting the thinnest \galvanizing agents." Capping by h-BN or graphene monolayers has also been shown to protect phosphorene from degradation [34, 39]. Similar There has been an unprecedented interest in layered to graphene, h-BN is a chemically inert material that can phosphorus allotropes as a new member of the family be exfoliated from bulk materials by mechanical transfer of two-dimensional (2D) materials in the post-graphene [40{43] or can be synthesized by chemical vapor deposi- era [1, 2].
    [Show full text]
  • Physical Science Sample Scope and Sequence
    Physical Science Louisiana Sample Scope and Sequence for Science Instruction This scope and sequence document was developed to assist teachers with the implementation of the Louisiana Student Standards for Science. This tool is not full curriculum and will need to be further built out by science educators. It has been designed to help in the initial transition to the new standards. This document is considered a “living” document, as we believe that teachers and other educators will find ways to improve it as they use it. Please send feedback to [email protected] so that we may use your input when updating this tool. About the Sample Scope and Sequence Tools ........................................................................................... 2 Building out the Science Scope and Sequences for Classroom Instruction................................................ 3 How to Use the Anchor and Investigative Phenomena .................................................................. 3 Choosing an Anchor Phenomenon ................................................................................................. 3 Choosing Investigative Phenomena ................................................................................................ 4 Investigating the Phenomena ......................................................................................................... 4 Other Useful Questions When Designing a Sequence of Learning ................................................ 4 Physical Science Standards Overview ........................................................................................................
    [Show full text]
  • Chapter 20 the Representative Elements
    Chapter 20 The Representative Elements Copyright ©2017 Cengage Learning. All Rights Reserved. Chapter 19 Table of Contents . (20.1) A survey of the representative elements . (20.2) The group 1A elements . (20.3) The chemistry of hydrogen . (20.4) The group 2A elements . (20.5) The group 3A elements . (20.6) The group 4A elements . (20.7) The group 5A elements . (20.8) The chemistry of nitrogen Copyright ©2017 Cengage Learning. All Rights Reserved. Chapter 19 Table of Contents . (20.9) The chemistry of phosphorus . (20.10) The group 6A elements . (20.11) The chemistry of oxygen . (20.12) The chemistry of sulfur . (20.13) The group 7A elements . (20.14) The group 8A elements Copyright ©2017 Cengage Learning. All Rights Reserved. Section 20.1 A Survey of the Representative Elements Reviewing the Periodic Table . Representative elements: Chemical properties are determined by the valence-level s and p electrons . Designated Groups 1A–8A . Transition metals: Result from the filling of d orbitals . Present at the center of the periodic table Copyright ©2017 Cengage Learning. All Rights Reserved. Copyright © Cengage Learning. All rights reserved 4 Section 20.1 A Survey of the Representative Elements Reviewing the Periodic Table (Continued) . Lanthanides: Correspond to the filling of the 4f orbitals . Actinides: Correspond to the filling of the 5f orbitals . Metalloids (semimetals): Elements along the division line between metals and nonmetals in the periodic table . Exhibit both metallic and nonmetallic characteristics Copyright ©2017 Cengage Learning. All Rights Reserved. Copyright © Cengage Learning. All rights reserved 5 Section 20.1 A Survey of the Representative Elements Differentiating Metals from Nonmetals Metals Nonmetals • Form cations by losing • Form anions by gaining valence electrons electrons • Exhibit electron • Exhibit electron configuration of the configuration of the noble gas from the noble gas in the same preceding period period Copyright ©2017 Cengage Learning.
    [Show full text]
  • A General-Purpose Machine-Learning Force Field for Bulk And
    ARTICLE https://doi.org/10.1038/s41467-020-19168-z OPEN A general-purpose machine-learning force field for bulk and nanostructured phosphorus ✉ Volker L. Deringer 1 , Miguel A. Caro 2,3 & Gábor Csányi 4 Elemental phosphorus is attracting growing interest across fundamental and applied fields of research. However, atomistic simulations of phosphorus have remained an outstanding challenge. Here, we show that a universally applicable force field for phosphorus can be 1234567890():,; created by machine learning (ML) from a suitably chosen ensemble of quantum-mechanical results. Our model is fitted to density-functional theory plus many-body dispersion (DFT + MBD) data; its accuracy is demonstrated for the exfoliation of black and violet phosphorus (yielding monolayers of “phosphorene” and “hittorfene”); its transferability is shown for the transition between the molecular and network liquid phases. An application to a phosphorene nanoribbon on an experimentally relevant length scale exemplifies the power of accurate and flexible ML-driven force fields for next-generation materials modelling. The methodology promises new insights into phosphorus as well as other structurally complex, e.g., layered solids that are relevant in diverse areas of chemistry, physics, and materials science. 1 Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, Oxford OX1 3QR, UK. 2 Department of Electrical Engineering and Automation, Aalto University, Espoo 02150, Finland. 3 Department of Applied Physics, Aalto University, Espoo 02150, Finland. 4 Engineering Laboratory, ✉ University of Cambridge, Cambridge CB2 1PZ, UK. email: [email protected] NATURE COMMUNICATIONS | (2020) 11:5461 | https://doi.org/10.1038/s41467-020-19168-z | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-020-19168-z he ongoing interest in phosphorus1 is partly due to its general reference database can be constructed by starting from an highly diverse allotropic structures.
    [Show full text]
  • BCA Schedule
    C Chemistry C38E C Chemistry Chemistry C * Chemical phenomena and the associated human activities Science of science of chemistry C29 X focused upon them, treated at the most general level. C2A * For applied chemistry, see Process industrial technology . Philosophy of chemistry (in Class U/V). An alternative location (not C2L X . Scientific method in chemistry * recommended) for applied chemistry is provided at CY Methodology in the most abstract sense. * for libraries wishing to collocate the technology with For practical methods and procedures, see C36. chemistry in Class C. C2M . Mathematics in chemistry C2 . Common subdivisions C2V J .. Topology in chemistry * Add to C2 numbers 2/9 in Auxiliary Schedule 1 with C2X . Statistics & probability in chemistry the same additions & modifications as in AY2 2/9; eg General operations & agents in chemistry C22 .. Forms of presentation * Add to C numbers & letters 2YM/82D following AY, C23 G ... Serials with the modifications indicated at C33/34. P ... Technical data C2Y Q . Organization & management of work in chemistry .. Persons in the subject QS .. Operational research C24 ... Chemists * See also Biography C29 2 C33 Common properties C .... Profession of chemistry D . Distribution * For education & training, see C26 A. W . Continuity C25 .. Organizations in chemistry X . Conditions L .. Communication & information in chemistry Y5 .. Electric field LO ... Terminology YG .. Systems characteristics * For nomenclature, see compounds CGH 25L O. C34 . Theoretical chemistry P ... Documentation in chemistry * As distinct from practical chemistry. Classify more VA .... Information services in chemistry specifically if possible. The term is sometimes used VB ..... Computerized information services as synonymous with quantum chemistry (see C26 A .
    [Show full text]
  • CHEM 1000 Lecture 32: Group 15 (Pnictogens)
    Sodium, Na Gallium, Ga CHEMISTRY 1000 Topic #2: The Chemical Alphabet Fall 2020 Dr. Susan Findlay See Exercises 11.1 to 11.4 Forms of Carbon The Group 15 Elements What do we know about the Group 15 elements? is diatomic; , and have multiple allotropes Nonmetal ( , ), metalloid ( , ) or metal ( ) They form one monoatomic anion (-3) and also exist They3+ have five3+ valence electrons (valence electron configuration . ) and positive electron affinities 2 3 Melting Boiling State Density Point Point (at 20 °C) (at 20 °C) Nitrogen -210 °C -196 °C Gas 0.00125 g/cm3 Phosphorus (white) 44 °C 280.5 °C Solid 2.2 g/cm3 Arsenic (grey) 817 °C* 616 °C* Solid 5.78 g/cm3 Antimony (grey) 631 °C 1635 °C Solid 6.69 g/cm3 Bismuth 271 °C 1580 °C Solid 9.75 g/cm3 2 Images from http://www.theodoregray.com/PeriodicTableDisplay/ Nitrogen Nitrogen is a very stable diatomic molecule ( ). The triple bond holding the two atoms together2 is very strong, so is a very unreactive gas. Nitrogen is often used as an inert atmosphere for chemical 2 reactions and for production of electronic components. Being the major component of air, it is much cheaper than the most common alternative, argon. (Air is 78% , 21% and 1% with traces of many other gases.) 2 2 As we saw earlier in the course, nitrogen will react spontaneously with lithium and with the alkaline earth metals: 3 Nitrogen The reaction between nitrogen and hydrogen is exothermic, but the activation energy is high, so it will not proceed without some sort of catalyst.
    [Show full text]