DOCSLIB.ORG

Quasicrystals: a Brief History of the Impossible

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Quasicrystals: a Brief History of the Impossible Rend. Fis. Acc. Lincei (2013) 24 (Suppl 1):S85–S91 DOI 10.1007/s12210-012-0203-3 X-RAY DIFFRACTION Quasicrystals: a brief history of the impossible Paul J. Steinhardt Received: 25 July 2012 / Accepted: 27 August 2012 / Published online: 15 September 2012 Ó Accademia Nazionale dei Lincei 2012 Abstract The 30-year history of quasicrystals is one in as a brief personal perspective rather than a formal history. which, time after time, the conventional scientific view Over 11,000 papers have been written on this subject by about what is possible has been proven wrong. First, other authors whose important contributions to the field quasicrystals were thought to be mathematically impossi- could not be included in these few pages. I strongly com- ble; then, physically impossible; then, impossible unless mend the reader to reviews and other reminiscences to synthesised in the laboratory under carefully controlled obtain a complete account. conditions. One by one, these strongly held views have been disproven, the last only recently as the result of the discovery of a natural quasicrystal found in a meteorite 1 Mathematically impossible dating back to the formation of the solar system. This paper is a brief personal perspective on this history of misun- When the concept of quasicrystals was first introduced in derstanding and discovery. 1984 (Levine and Steinhardt 1984), it met resistance because it appeared to contradict mathematical theorems Keywords Quasicrystals Á Icosahedral symmetry Á that had been proven over the last two centuries and that Diffraction Á Icosahedrite had been adopted as essential truths in crystallography and solid state physics. Solids were thought to come in one of two forms, ordered and disordered, where ordered meant This pre´cis is based on a presentation delivered at the periodic and disordered meant amorphous or glassy. Accademia dei Lincei for a meeting commemorating the (Incommensurate crystals were known, but they are subject 100th anniversary of X-ray diffraction. The topic was to the same symmetry restrictions as periodic crystals.) The quasicrystals, a subject that has captivated me for over classic theorems of Schoenflies and Fyodorov proven in the 30 years with its never-ending ability to surprise. The 19th century established that periodic solids are only recent awarding of the Nobel Prize in Chemistry to Dan allowed two-, three-, four-, or sixfold symmetry axes, Shechtman for his discovery of the first icosahedral solid limiting the number of possibilities in three dimensions to and the centenary of X-ray diffraction made this a timely 32 point groups. Five-, seven- and all higher-order sym- occasion for a historical reflection. This essay is intended metry axes—an infinite number of possibilities—are incompatible with periodicity. Most forbidden of all is icosahedral symmetry, because it contains six independent This contribution is the written, peer-reviewed version of a paper presented at the conference ‘‘The Centennial of X-Ray Diffraction disallowed fivefold symmetry axes, the maximum number (1912–2012)’’, held at Accademia Nazionale dei Lincei in Roma on possible in three dimensions. The historic work of von May 8 and 9, 2012. Laue and the Braggs showed that periodic solids exhibit point-like (Bragg) diffraction patterns with the same sym- & P. J. Steinhardt ( ) metry restrictions. By contrast, amorphous solids and Department of Physics, Princeton Center for Theoretical Science, Princeton University, Princeton, NJ 08544, USA glasses have isotropic diffuse diffraction patterns. All this e-mail: [email protected] is rigorously true. 123 S86 Rend. Fis. Acc. Lincei (2013) 24 (Suppl 1):S85–S91 Somehow, after several decades, point-like diffraction, be some analogy for solids [Conway (unpublished); Mac- order, and crystal became incorrectly conflated as mathe- kay 1981, 1982; Kramer and Neri 1984; Elser 1986], matically equivalent. This was the conventional belief in though in most cases it was not made clear what this meant. 1981 when quasicrystals began to emerge as a hypothetical The approach in Levine and Steinhardt 1984 was system- idea. Now, after quasicrystals, it is recognized that the atic in first identifying the precise symmetries and order terms are inequivalent, though the field has not yet parameters that underlie the Penrose tiling and can be used broadened its view as much as it needs to, as discussed in to define a new phase of matter, namely quasiperiodicity the concluding remarks. and bond orientational order, and then showing that they A small crack in the establishment view came with the generalize to arbitrary non-crystallographic symmetries in theory of dislocation-mediated two-dimensional melting by two and three dimensions. Nelson and Halperin (1979), in which they argued for a Icosahedral symmetry became the first target. A three- two-stage melting process from crystal to liquid punctuated dimensional quasicrystal was constructed using polyhedral by an intermediate ‘‘hexatic phase’’. Hexatic diffraction units and certain ‘‘face-to-face matching’’ rules that force a is neither Bragg nor simply diffuse; rather the pattern quasiperiodic arrangement with perfect long-range icosa- consists of a hexagonal arrangement of algebraically hedral orientational order. The existence of matching rules decaying finite-width peaks. The rotational symmetry is not was an important advance because it meant that, conceiv- remarkable, since it is crystallographically allowed, but the ably, local interactions (e.g., between atoms or molecules) introduction of a ‘‘bond orientational order parameter’’ is, could be sufficient to make the new phase a ground state. The since it opens the possibility of a new type of ordered phase hypothetical phase was ultimately dubbed quasicrystal, that had not been considered previously for monatomic short for quasiperiodic crystal (Levine and Steinhardt 1984). systems. The mathematical properties are subtle. In real space, In a study with David Nelson and Marco Ronchetti the lack of periodicity means that there is no translation of (Steinhardt et al. 1981), we examined whether a similar a quasicrystal pattern that exactly overlays the original; effect occurs in three-dimensional supercooled liquids and consequently, each atom or cluster of atoms in a quasi- glasses composed of a single type atom with Lennard– crystal has a distinct global arrangement of atoms sur- Jones interactions. Earlier, Nelson and Toner (1981) had rounding it. On the other hand, there is a sequence of proposed the possibility of a cubatic bond orientationally translations of the pattern that almost overlay the original ordered phase, and the original intent of the investigation except for a small density of misalignments; and that was to search for it. The effort failed, but something density can be made arbitrarily small by going to ever curious turned up instead: icosahedral bond orientational larger translations. This is the closest to translational order extending many interatomic spacings. This was not a symmetry without being periodic. Similarly, there is new phase, since the icosahedral correlations only spanned sequence of points such that a rotation by 2p/5 about the a finite distance, but it introduced a new element: crystal- point almost overlaps the original (see Steinhardt and Bindi lographically forbidden symmetry. 2012 for illustrations of these properties). In a colloquium given in fall 1981, shortly after joining In reciprocal space, the almost translational symmetry the faculty at the University of Pennsylvania, the hypoth- guarantees a diffraction pattern consisting only of true esis was floated that, by including two or more atomic point-like peaks just like the Bragg peaks in a periodic species, it may be possible to have a truly new phase of crystal. The peaks are arranged in a reciprocal space lattice matter with infinite-range icosahedral bond orientational of points described by an integer sum of basis vectors set order that evades the crystallographic theorems. In the by the rotational symmetry, just as for periodic crystals, but audience was a young graduate student, Dov Levine, who with a symmetry that is forbidden to crystals. However, approached afterward to ask if he could join in pursuing unlike the case for crystals, the number of integer linearly this idea. Warnings that the project was highly risky and independent basis vectors D in d-dimensions exceeds d, may have not physical relevance did not deter him, and so resulting in a reciprocal lattice with a dense arrangement of the quest started. peaks labeled by D quasi-Miller indices. For example, the Within a matter of months, the concept of quasicrystals reciprocal lattice for three-dimensional icosahedral quasi- developed. An inspiration was the two-dimensional crystals has D = 6 quasi-Miller indices. The result is a Penrose tiling invented by Sir Roger Penrose (Penrose diffraction pattern that is distinctive and instantaneously 1974) 7 years earlier. Penrose had identified a pair of tile recognizable. shapes that can only fit together non-periodically, forming An important corollary is that the real space structure can a self-similar pattern full of fivefold symmetric clusters of be viewed as a projection or cut through a subset of points in a tiles. Penrose’s tiling attracted the attention of diverse six-dimensional hypercubic lattice; and the diffraction theorists; several independently speculated that there might pattern can be computed as the convolution of the 123 Rend. Fis. Acc. Lincei (2013) 24 (Suppl 1):S85–S91
Load more

Recommended publications
  • WHAT IS...A Quasicrystal?, Volume 53, Number 8
    ?WHAT IS... a Quasicrystal? Marjorie Senechal The long answer is: no one is sure. But the short an- diagrams? The set of vertices of a Penrose tiling does— swer is straightforward: a quasicrystal is a crystal that was known before Shechtman’s discovery. But with forbidden symmetry. Forbidden, that is, by “The what other objects do, and how can we tell? The ques- Crystallographic Restriction”, a theorem that confines tion was wide open at that time, and I thought it un- the rotational symmetries of translation lattices in two- wise to replace one inadequate definition (the lattice) and three-dimensional Euclidean space to orders 2, 3, with another. That the commission still retains this 4, and 6. This bedrock of theoretical solid-state sci- definition today suggests the difficulty of the ques- ence—the impossibility of five-fold symmetry in crys- tion we deliberately but implicitly posed. By now a tals can be traced, in the mineralogical literature, back great many kinds of aperiodic crystals have been to 1801—crumbled in 1984 when Dany Shechtman, a grown in laboratories around the world; most of them materials scientist working at what is now the National are metals, alloys of two or three kinds of atoms—bi- Institute of Standards and Technology, synthesized nary or ternary metallic phases. None of their struc- aluminium-manganese crystals with icosahedral sym- tures has been “solved”. (For a survey of current re- metry. The term “quasicrystal”, hastily coined to label search on real aperiodic crystals see, for example, the such theretofore unthinkable objects, suggests the website of the international conference ICQ9, confusions that Shechtman’s discovery sowed.
    [Show full text]
  • Quasicrystals a New Kind of Symmetry Sandra Nair First, Definitions
    Quasicrystals A new kind of symmetry Sandra Nair First, definitions ● A lattice is a poset in which every element has a unique infimum and supremum. For example, the set of natural numbers with the notion of ordering by magnitude (1<2). For our purposes, we can think of an array of atoms/molecules with a clear sense of assignment. ● A Bravais lattice is a discrete infinite array of points generated by linear integer combinations of 3 independent primitive vectors: {n1a1 + n2a2 + n3a3 | n1, n2, n3 ∈ Z}. ● Crystal structures = info of lattice points + info of the basis (primitive) vectors. ● Upto isomorphism of point groups (group of isometries leaving at least 1 fixed point), 14 different Bravais lattice structures possible in 3D. Now, crystals... ● Loosely speaking, crystals are molecular arrangements built out of multiple unit cells of one (or more) Bravais lattice structures. ● Crystallographic restriction theorem: The rotational symmetries of a discrete lattice are limited to 2-, 3-, 4-, and 6-fold. ● This leads us to propose a “functional” definition: A crystal is a material that has a discrete diffraction pattern, displaying rotational symmetries of orders 2, 3, 4 and 6. ● Note: Order 5 is a strictly forbidden symmetry → important for us. Tessellations aka tilings Now that we have diffraction patterns to work with, we consider the question of whether a lattice structure tiles or tessellates the plane. This is where the order of the symmetry plays a role. The crystals are special, as they display translational symmetries. As such, the tiling of their lattice structures (which we could see thanks to diffraction patterns) are periodic- they repeat at regular intervals.
    [Show full text]
  • A Review of Transmission Electron Microscopy of Quasicrystals—How Are Atoms Arranged?
    crystals Review A Review of Transmission Electron Microscopy of Quasicrystals—How Are Atoms Arranged? Ruitao Li 1, Zhong Li 1, Zhili Dong 2,* and Khiam Aik Khor 1,* 1 School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; [email protected] (R.L.); [email protected] (Z.L.) 2 School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore * Correspondence: [email protected] (Z.D.); [email protected] (K.A.K.); Tel.: +65-6790-6727 (Z.D.); +65-6592-1816 (K.A.K.) Academic Editor: Enrique Maciá Barber Received: 30 June 2016; Accepted: 15 August 2016; Published: 26 August 2016 Abstract: Quasicrystals (QCs) possess rotational symmetries forbidden in the conventional crystallography and lack translational symmetries. Their atoms are arranged in an ordered but non-periodic way. Transmission electron microscopy (TEM) was the right tool to discover such exotic materials and has always been a main technique in their studies since then. It provides the morphological and crystallographic information and images of real atomic arrangements of QCs. In this review, we summarized the achievements of the study of QCs using TEM, providing intriguing structural details of QCs unveiled by TEM analyses. The main findings on the symmetry, local atomic arrangement and chemical order of QCs are illustrated. Keywords: quasicrystal; transmission electron microscopy; symmetry; atomic arrangement 1. Introduction The revolutionary discovery of an Al–Mn compound with 5-fold symmetry by Shechtman et al. [1] in 1982 unveiled a new family of materials—quasicrystals (QCs), which exhibit the forbidden rotational symmetries in the conventional crystallography.
    [Show full text]
  • Some Considerations Relating to the Dynamics of Quasicrystals
    Some considerations relating to the dynamics of quasicrystals M. Pitk¨anen Email: [email protected]. http://tgdtheory.com/public_html/. November 12, 2012 Contents 1 The dynamics of quasicrystals, the dynamics of K¨ahleraction, symbolic dynamics, and the dynamics of self-organization 1 1.1 The non-determinism for the dynamics of quasicrystals contra non-determinism of K¨ahleraction . .1 1.2 The dynamics of quasicrystals as a model for fundamental dynamics or high level sym- bolic dynamics? . .2 1.3 Could ordered water layers around biomolecules be modelled as quasicrystal like structure?3 2 What could be the variational principle behind self-organization? 4 2.1 Why Negentropy Maximization Principle should favor quasicrystals? . .5 2.2 Maximal capacity to represent information with minimal metabolic energy costs as a basic variational principle? . .5 2.3 A possible realization for 4-D dynamics favoring quasicrystal like structures . .6 2.4 Summary . .7 1 The dynamics of quasicrystals, the dynamics of K¨ahlerac- tion, symbolic dynamics, and the dynamics of self-organization The dynamics of quasicrystals looks to me very interesting because it shares several features of the dynamics of K¨ahleraction defining the basic variational principle of classical TGD and defining the dynamics of space-time surfaces. In the following I will compare the basic features of the dynamics of quasicrystals to the dynamics of preferred extremals of K¨ahleraction [K1]. Magnetic body carrying dark matter is the fundamental intentional agent in TGD inspired quantum biology and the cautious proposal is that magnetic flux sheets could define the grid of 3-planes (or more general 3-surfaces) defining quasi-periodic background fields favoring 4-D quasicrystals or more general structures in TGD Universe.
    [Show full text]
  • Thirty-Fourth List of New Mineral Names
    MINERALOGICAL MAGAZINE, DECEMBER 1986, VOL. 50, PP. 741-61 Thirty-fourth list of new mineral names E. E. FEJER Department of Mineralogy, British Museum (Natural History), Cromwell Road, London SW7 5BD THE present list contains 181 entries. Of these 148 are Alacranite. V. I. Popova, V. A. Popov, A. Clark, valid species, most of which have been approved by the V. O. Polyakov, and S. E. Borisovskii, 1986. Zap. IMA Commission on New Minerals and Mineral Names, 115, 360. First found at Alacran, Pampa Larga, 17 are misspellings or erroneous transliterations, 9 are Chile by A. H. Clark in 1970 (rejected by IMA names published without IMA approval, 4 are variety because of insufficient data), then in 1980 at the names, 2 are spelling corrections, and one is a name applied to gem material. As in previous lists, contractions caldera of Uzon volcano, Kamchatka, USSR, as are used for the names of frequently cited journals and yellowish orange equant crystals up to 0.5 ram, other publications are abbreviated in italic. sometimes flattened on {100} with {100}, {111}, {ill}, and {110} faces, adamantine to greasy Abhurite. J. J. Matzko, H. T. Evans Jr., M. E. Mrose, lustre, poor {100} cleavage, brittle, H 1 Mono- and P. Aruscavage, 1985. C.M. 23, 233. At a clinic, P2/c, a 9.89(2), b 9.73(2), c 9.13(1) A, depth c.35 m, in an arm of the Red Sea, known as fl 101.84(5) ~ Z = 2; Dobs. 3.43(5), D~alr 3.43; Sharm Abhur, c.30 km north of Jiddah, Saudi reflectances and microhardness given.
    [Show full text]
  • Aperiodic Mineral Structures
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Infoscience - École polytechnique fédérale de Lausanne EMU Notes in Mineralogy, Vol. 19 (2017), Chapter 5, 213–254 Aperiodic mineral structures L. BINDI1 and G. CHAPUIS2 1 Dipartimento di Scienze della Terra, Universita` di Firenze, Via La Pira 4, I-50121 Firenze, Italy 2 Laboratoire de Cristallographie, E´cole Polytechnique Fe´de´rale de Lausanne, CH-1015 Lausanne, Switzerland The three-dimensional periodic nature of crystalline structures was so strongly anchored in the minds of scientists that the numerous indications that seemed to question this model struggled to acquire the status of validity. The discovery of aperiodic crystals, a generic term including modulated, composite and quasicrystal structures, started in the 1970s with the discovery of incommensurately modulated structures and the presence of satellite reflections surrounding the main reflections in the diffraction patterns. The need to use additional integers to index such diffractograms was soon adopted and theoretical considerations showed that any crystal structure requiring more than three integers to index its diffraction pattern could be described as a periodic object in a higher dimensional space, i.e. superspace, with dimension equal to the number of required integers. The structure observed in physical space is thus a three-dimensional intersection of the structure described as periodic in superspace. Once the symmetry properties of aperiodic crystals were established, the superspace theory was soon adopted in order to describe numerous examples of incommensurate crystal structures from natural and synthetic organic and inorganic compounds even to proteins. Aperiodic crystals thus exhibit perfect atomic structures with long-range order, but without any three-dimensional translational symmetry.
    [Show full text]
  • Previously Unknown Quasicrystal Periodic Approximant Found in Space Received: 13 August 2018 Luca Bindi 1, Joyce Pham 2 & Paul J
    www.nature.com/scientificreports OPEN Previously unknown quasicrystal periodic approximant found in space Received: 13 August 2018 Luca Bindi 1, Joyce Pham 2 & Paul J. Steinhardt3,4 Accepted: 16 October 2018 We report the discovery of Al Ni Fe , the frst natural known periodic crystalline approximant Published: xx xx xxxx 34 9 2 to decagonite (Al71Ni24Fe5), a natural quasicrystal composed of a periodic stack of planes with quasiperiodic atomic order and ten-fold symmetry. The new mineral has been approved by the International Mineralogical Association (IMA 2018-038) and ofcially named proxidecagonite, which derives from its identity to periodic approximant of decagonite. Both decagonite and proxidecagonite were found in fragments from the Khatyrka meteorite. Proxidecagonite is the frst natural quasicrystal approximant to be found in the Al-Ni-Fe system. Within this system, the decagonal quasicrystal phase has been reported to transform at ~940 °C to Al13(Fe,Ni)4, Al3(Fe,Ni)2 and the liquid phase, and between 800 and 850 °C to Al13(Fe,Ni)4, Al3(Fe,Ni) and Al3(Fe,Ni)2. The fact that proxidecagonite has not been observed in the laboratory before and formed in a meteorite exposed to high pressures and temperatures during impact-induced shocks suggests that it might be a thermodynamically stable compound at high pressure. The most prominent structural motifs are pseudo-pentagonal symmetry subunits, such as pentagonal bipyramids, that share edges and corners with trigonal bipyramids and which maximize shortest Ni–Al over Ni–Ni contacts. 1,2 Te frst decagonal quasicrystalline (QC) phase found in nature, decagonite Al71Ni24Fe5 , was discovered in the Khatyrka meteorite, a CV3 carbonaceous chondrite3–8.
    [Show full text]
  • 79Th Annual Meeting of the Meteoritical Society (2016) 6017.Pdf
    79th Annual Meeting of the Meteoritical Society (2016) 6017.pdf DISCOVERY OF NEW Al-Cu-Fe MINERALS IN THE KHATYRKA CV3 METEORITE. Chi Ma1,*, Chaney Lin2, Luca Bindi3, Paul J. Steinhardt2. 1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA; 2Department of Physics, Princeton University, Princeton, NJ 08544, USA; 3Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Florence, Italy; *Email: [email protected]. Introduction: During a nanomineralogy investigation of the Khatyrka CV3 carbonaceous chondrite, we have identified two new alloy minerals (AlCu with a Pm-3m CsCl structure and Al3Fe with a C2/m structure) and associ- ated icosahedrite (quasicrystal Al63Cu26Fe11 with a five-fold symmetry) at micron scales in section 126A of USNM 7908. The section belongs to the larger Grain 126, which is one of the fragments recovered from an expedition to the Koryak Mountains in far eastern Russia in 2011 [1] as a result of a search for samples that would provide infor- mation on the origin of the quasicrystal mineral icosahedrite [2,3,4]. The recovered fragments have meteoritic (CV3- like) oxygen isotopic compositions and are identified collectively as coming from the Khatyrka meteorite [5], which formed 4.5 billion years ago during the earliest stages of the solar system. Khatyrka is unique, so far being the only meteorite to host metallic Al component. Field-emission scanning electron microscope with energy-dispersive X-ray spectrometer and electron back- scatter diffraction (EBSD), and electron probe microanalyzer (EPMA) were used to characterize chemical composi- tions and structures of the minerals in section 126A.
    [Show full text]
  • Cosmic History and a Candidate Parent Asteroid for the Quasicrystal-Bearing Meteorite Khatyrka
    COSMIC HISTORY AND A CANDIDATE PARENT ASTEROID FOR THE QUASICRYSTAL-BEARING METEORITE KHATYRKA Matthias M. M. Meier1*, Luca Bindi2,3, Philipp R. Heck4, April I. Neander5, Nicole H. Spring6,7, My E. I. Riebe1,8, Colin Maden1, Heinrich Baur1, Paul J. Steinhardt9, Rainer Wieler1 and Henner Busemann1 1Institute of Geochemistry and Petrology, ETH Zurich, Zurich, Switzerland. 2Dipartimento di Scienze della Terra, Università di Firenze, Florence, Italy. 3CNR-Istituto di Geoscienze e Georisorse, Sezione di Firenze, Florence, Italy. 4Robert A. Pritzker Center for Meteoritics and Polar Studies, Field Museum of Natural History, Chicago, USA. 5De- partment of Organismal Biology and Anatomy, University of Chicago, Chicago, USA. 6School of Earth and Environ- mental Sciences, University of Manchester, Manchester, UK. 7Department of Earth and Atmospheric Sciences, Uni- versity of Alberta, Edmonton, Canada. 8Current address: Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, USA. 9Department of Physics, and Princeton Center for Theoretical Science, Princeton University, Princeton, USA. *corresponding author: [email protected]; (office phone: +41 44 632 64 53) Submitted to Earth and Planetary Science Letters. Abstract The unique CV-type meteorite Khatyrka is the only natural sample in which “quasicrystals” and associated crystalline Cu,Al-alloys, including khatyrkite and cupalite, have been found. They are suspected to have formed in the early Solar System. To better understand the origin of these ex- otic phases, and the relationship of Khatyrka to other CV chondrites, we have measured He and Ne in six individual, ~40-μm-sized olivine grains from Khatyrka. We find a cosmic-ray exposure age of about 2-4 Ma (if the meteoroid was <3 m in diameter, more if it was larger).
    [Show full text]
  • EXPERIMENTAL IMPACTS of ALUMINUM PROJECTILES INTO QUARTZ SAND: FORMATION 1,2 1,3 of KHATYRKITE (Cual2) and REDUCTION of QUARTZ to SILICON
    Bridging the Gap III (2015) 1071.pdf EXPERIMENTAL IMPACTS OF ALUMINUM PROJECTILES INTO QUARTZ SAND: FORMATION 1,2 1,3 OF KHATYRKITE (CuAl2) AND REDUCTION OF QUARTZ TO SILICON. C. Hamann , D. Stöffler , and W. U. Reimold1,3. 1Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, In- validenstraße 43, 10115 Berlin, Germany ([email protected]; dieter.stö[email protected]; [email protected]); 2Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteserstraße 74– 100, 12249 Berlin, Germany, 3Humboldt-Universität zu Berlin, Unter der Linden 6, 10099 Berlin, Germany. Introduction and Rationale: Impact cratering is a melt particles, shock-lithified sand with and without basic geologic process in the solar system, which was distinct shock effects (PDF, diaplectic glass), and frac- predominant over endogenic geologic processes in the tured quartz grains (for details, see the companion early evolution of geologically active planetary bodies. abstract by Wünnemann et al. [10]). Since this study Since most planetary surfaces are highly porous and/or focuses on chemical projectile–target interaction, we composed of non-cohesive materials (e.g., the lunar will only consider impact melt particles that obviously regolith), understanding the influence of pore space show a crust of projectile melt on their top sides. and non-cohesiveness of materials on the impact pro- The bulk compositions of projectile and target were cess is crucial for gaining insights into the evolution of determined with EMPA and XRF, respectively. Impact planetary regoliths. To this end, numerous theoretical melt particles were studied with optical microscopy, and experimental studies have been conducted (e.g., SEM-EDX, and EMPA.
    [Show full text]
  • Design Rules for Discovering 2D Materials from 3D Crystals
    Design Rules for Discovering 2D Materials from 3D Crystals by Eleanor Lyons Brightbill Collaborators: Tyler W. Farnsworth, Adam H. Woomer, Patrick C. O'Brien, Kaci L. Kuntz Senior Honors Thesis Chemistry University of North Carolina at Chapel Hill April 7th, 2016 Approved: ___________________________ Dr Scott Warren, Thesis Advisor Dr Wei You, Reader Dr. Todd Austell, Reader Abstract Two-dimensional (2D) materials are championed as potential components for novel technologies due to the extreme change in properties that often accompanies a transition from the bulk to a quantum-confined state. While the incredible properties of existing 2D materials have been investigated for numerous applications, the current library of stable 2D materials is limited to a relatively small number of material systems, and attempts to identify novel 2D materials have found only a small subset of potential 2D material precursors. Here I present a rigorous, yet simple, set of criteria to identify 3D crystals that may be exfoliated into stable 2D sheets and apply these criteria to a database of naturally occurring layered minerals. These design rules harness two fundamental properties of crystals—Mohs hardness and melting point—to enable a rapid and effective approach to identify candidates for exfoliation. It is shown that, in layered systems, Mohs hardness is a predictor of inter-layer (out-of-plane) bond strength while melting point is a measure of intra-layer (in-plane) bond strength. This concept is demonstrated by using liquid exfoliation to produce novel 2D materials from layered minerals that have a Mohs hardness less than 3, with relative success of exfoliation (such as yield and flake size) dependent on melting point.
    [Show full text]
  • Evidence of Cross-Cutting and Redox Reaction in Khatyrka Meteorite
    www.nature.com/scientificreports OPEN Evidence of cross-cutting and redox reaction in Khatyrka meteorite reveals metallic-Al minerals formed Received: 5 December 2016 Accepted: 22 March 2017 in outer space Published: xx xx xxxx Chaney Lin1, Lincoln S. Hollister2, Glenn J. MacPherson3, Luca Bindi4,5, Chi Ma6, Christopher L. Andronicos7 & Paul J. Steinhardt1,8 We report on a fragment of the quasicrystal-bearing CV3 carbonaceous chondrite Khatyrka recovered from fine-grained, clay-rich sediments in the Koryak Mountains, Chukotka (Russia). We show higher melting-point silicate glass cross-cutting lower melting-point Al-Cu-Fe alloys, as well as unambiguous evidence of a reduction-oxidation reaction history between Al-Cu-Fe alloys and silicate melt. The redox reactions involve reduction of FeO and SiO2 to Fe and Fe-Si metal, and oxidation of metallic Al to Al2O3, occurring where silicate melt was in contact with Al-Cu-Fe alloys. In the reaction zone, there are metallic Fe and Fe-Si beads, aluminous spinel rinds on the Al-Cu-Fe alloys, and Al2O3 enrichment in the silicate melt surrounding the alloys. From this and other evidence, we demonstrate that Khatyrka must have experienced at least two distinct events: first, an event as early as 4.564 Ga in which the first Al-Cu-Fe alloys formed; and, second, a more recent impact-induced shock in space that led to transformations of and reactions between the alloys and the meteorite matrix. The new evidence firmly establishes that the Al-Cu-Fe alloys (including quasicrystals) formed in outer space in a complex, multi-stage process.
    [Show full text]