Mathematical Techniques in Crystallography and Materials

Total Page:16

File Type:pdf, Size:1020Kb

Mathematical Techniques in Crystallography and Materials book reviews Acta Crystallographica Section A Foundations of book reviews Crystallography Works intended for this column should be sent direct to the Book-Review Editor, whose address appears in this ISSN 0108-7673 issue. All reviews are also available from Crystallography Journals Online, supplemented where possible with direct links to the publisher's information. International tables for crystallography. The ®rst edition of ITA was reviewed by Nomenclature. Hence, unlike common texts Vol. A. 5th edition. Edited by Th. Hahn. Stadnicka et al.[Acta Cryst. (1987), A43, or tables, ITA is being continuously Pp. xx + 911. Dordrecht: Kluwer 156±159]. They concluded, after assessing all improved by a well organized and com- Academic Publishers, 2002. Price sections individually, that ITA is a clearly, petent community, whose recommendations, EUR 242, GBP 142, USD 225. ISBN thoroughly and coherently written book that after thorough discussion, are taken as input has been prepared carefully and is of good for subsequent editions. One example was 0-7923-6590-9. technical quality. an inconsistency in the concept of `symmetry The reader of ITA5 will ®rst notice a new element' [H. D. Flack et al. (2000). Acta Since its ®rst appearance in 1983, Volume A white (red)-green hard cover differing from Cryst. A56, 96±98], which has been removed of International Tables for Crystallography the blue (gold) predecessors, this time by de®ning the geometric element as a (hereafter ITA) has served `consumers' of without a book jacket. Although it looks labelled geometric item. Hence corrigenda symmetry-group data for about 20 years and more attractive at ®rst glance, the white part and addenda became necessary. Those of the has experienced, during a permanent dialog might lose its beauty more quickly. Then, third edition were summarized in Acta Cryst. with the readers, four more or less major looking at the layout of the interior, a (1995), A51, 592±595. revisions. ITA is the ®rst in a series of smaller font attracts the reader's attention Turning to changes of the crystallographic International Tables for Crystallography and which makes the arrangement of the text information supplied by ITA5 as compared treats one-, two- and three-dimensional more concise, because the number of lines to the previous edition, it should ®rst be crystallographic space groups. Extensions to per page is approximately maintained. mentioned that the incorporation of the `generalized symmetry' are beyond the Hence, more space between the subsections double-glide-plane symbol `e' into space- scope of this volume. A salient point of ITA along with an in-depth four-digit decimal group symbols has been completed is the adoption of an advanced level of classi®cation facilitates browsing ITA5 throughout the volume. This means that, in symmetry theory, which is strictly compat- considerably. The table of contents now addition to glide planes a, b, c, d, n used ible with the demands of computerization of covers 6 pages instead of 4 of the previous before 1995, a sixth symmetry element crystallographic problems. The Editor's goal edition. The plain rearrangement of the text appears in all parts (in centred cells only). to provide data that are useful for all aspects of the fourth edition is a noteworthy Secondly, subgroup and supergroup data of crystallography as well as text to satisfy achievement of ITA5 in itself. One compo- have been changed by adding space-group the needs of those interested in the theor- nent of that is bringing tables or ®gures numbers and rearranging the group symbols etical reasons behind these tables has led to closer to the place where they are quoted according to rising index and falling space- a fruitful combination of tables for practical ®rst. Moreover, instead of the creamy paper group number. This applies particularly to use in the ®rst part and a high-level textbook previously utilized, for the current edition Part 7 as the main part of ITA and facilitates in the second. ITA succeeded in proposing white paper has been used. Again this makes dealing with the various symbols. It is a compromise between competing view reading easier, apart from proper fractions recommended for future editions to obey points. I mention issues such as the hexag- which, due to the smaller font, appear a bit these rules in the examples of subgroups onal/trigonal versus rhombohedral sub- faint now. However, the general quality of given in Chapter 4.3 (by E. F. Bertaut), too. division and the so-called `monoclinic print is excellent. Thirdly, there are several improvements that monster', which, for the convenience of the Then a hidden change in ITA5 should be apply to individual groups only, such as reader, is a summary of all settings and cell mentioned, which will certainly become a changes in the sequence of the positions and choices of the monoclinic space groups. great advantage for future application symmetry operations for the `rhombohedral Because symmetry is the basis of crystal- compared to editions 1±4. It is the computer- axes' descriptions of certain R groups. While lography, previous editions of ITA had to be based production of ITA5, accomplished by changes of Parts 1, 3±6, 11±13 (by Th. Hahn, reissued several times: 1st edition 1983, M. I. Aroyo and P. B. Konstantinov. All A. Looijenga-Vos, M. J. Buerger, E. F. reprinted with corrections 1984, 2nd revised space-group tables were reprogrammed, Bertaut, H. Arnold, W. Fischer, E. Koch, edition 1987, 2nd revised edition reprinted whereas the space-group diagrams were H. Burzlaff, H. Zimmermann, Y. Billiet) with corrections 1989, 3rd revised edition scanned from the existing presentations, are mainly of formal character, substantial 1992, 4th revised edition 1995, 4th revised which in turn had been improved several revisions and reorganizations of the text edition reprinted with corrections 1996, 4th times over the years. One promising future have been carried out in the remaining parts. edition reprinted 1998, 5th revised edition option of this computerization is the linking They can in most cases be considered 2002. The volume has increased from xv + of ITA5 to other volumes of this series. successful in expressing the fundamentals 854 pages in 1983 to xx + 911 pages in 2002. Because ITA is published for the Inter- more clearly, apparently stimulated by the This 5th edition (ITA5) is more extensively national Union of Crystallography (IUCr), feedback from students, and in taking new revised than any of the preceding editions. its content has been the subject of perma- developments into account. While the number of parts (15) is main- nent attention by Commissions of the IUCr, Examples are the presentation of general tained in ITA5, the number of authors has in particular by the Commission on Inter- and special re¯ection conditions (Section increased. national Tables and the Commission on 2.2.13) and the way monoclinic space groups Acta Cryst. (2004). A60, 641±642 641 book reviews are treated (Section 2.2.16), both by Th. relevant symbols, ITA delivers not only the Crystal structure determination. By Hahn & A. Looijenga-Vos. The text of Part 8 complete listings but also a comprehensive Werner Massa. Second completely (by H. Wondratschek) has been updated to explanation of the theory behind them and updated edition. Pp. XI + 210. Berlin, bridge the gap to topics that are not the detailed instructions for use. Hence, it is Heidelberg, New York: Springer-Verlag, subject of ITA but are of current interest to indispensable for people dealing with the 2004. Price EUR 48.10. ISBN 3 540 crystallographers, like symmetry in spaces of symmetry of crystals. The present revised 20644 2. dimension >3 and incommensurate struc- edition, ITA5, is another step towards tures, as well as to topics which have now minimization of inaccuracies and improve- been dealt with comprehensively in subse- ment of readability. Chapters of different A review of the ®rst edition of this book was quent volumes of the International Tables authors of ITA5 have become more homo- published in the May 2001 issue of Acta series, like subperiodic groups. The concept geneous by cross references and due to the Cryst. A57, page 368. The second edition has of a `lattice system of space groups' and its rearrangement of topics between them. I been considerably updated, especially the relationship to Bravais ¯ocks and the have been strikingly unsuccessful in the chapter on experimental methods, which is concept of `normalizers of space groups' has search for errors. Minor ¯aws (some now mainly concerned with modern data been worked out in a much clearer manner mentioned above) may readily be corrected. collection using area detectors. Many tips in the revised formulation. With regard to Being published in the 21st century, historic and insights help readers to recognise and normalizers, `special topics' have been remarks like `something is known since the avoid possible errors and traps, and to judge removed in view of the extended Part 15. last century' (e.g. on p. 738) should now the quality of results. Part 9 on crystal lattices has been better read ` ... since the 19th century' to enlarged by a new chapter on the Delaunay avoid further corrections in 2102. I feel reduction (by H. Burzlaff & H. Zimmer- personal indebtedness to the Editor and to mann) and by a chapter on `further proper- the other authors of this useful volume and ties of lattices', where B. Gruber deals with the huge work that has been done. Buerger cells, lattice characters and sublat- Mathematical techniques in crystallog- Peter Paufler tices of n-dimensional lattices. The former raphy and materials science. By Edward authors contribute also a list of the 24 Chair of Crystallography Prince. 3rd ed. Pp.
Recommended publications
  • Nano-Characterization of Ceramic-Metallic Interpenetrating Phase Composite Material Using Electron Crystallography
    YOUNGSTOWN STATE UNIVERSITY Nano-Characterization of Ceramic-Metallic Interpenetrating Phase Composite Material using Electron Crystallography by Marjan Moro Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in Engineering in the Mechanical Engineering Program Mechanical and Industrial Engineering May 2012 Nano-Characterization of Ceramic-Metallic Interpenetrating Phase Composite Material using Electron Crystallography by Marjan Moro I hereby release this thesis to the public. I understand that this thesis will be made available from the OhioLINK ETD Center and the Maag Library Circulation Desk for public access. I also authorize the University or other individuals to make copies of this thesis as needed for scholarly research. Signature: Marjan Moro, Student Date Approvals: Dr. Virgil C. Solomon, Thesis Advisor Date Dr. Matthias Zeller, Committee Member Date Dr. Timothy R. Wagner, Committee Member Date Dr. Hyun W. Kim, Committee Member Date Dr. Peter J. Kasvinsky, Dean of Graduate Studies Date i Abstract Interpenetrating phase composites (IPCs) have unique mechanical and physical proper- ties and thanks to these they could replace traditional single phase materials in numbers of applications. The most common IPCs are ceramic-metallic systems in which a duc- tile metal supports a hard ceramic making it an excellent composite material. Fireline, Inc., from Youngstown, OH manufactures such IPCs using an Al alloy-Al2O3 based ceramic-metallic composite material. This product is fabricated using a Reactive Metal Penetration (RMP) process to form two interconnected networks. Fireline products are used, among others, as refractory materials for handling of high temperature molten metals. A novel route to adding a shape memory metal phase within a ceramic matrix has been proposed.
    [Show full text]
  • Division of Academic Affairs Technology Fee – Project Proposal 2015
    Division of Academic Affairs Technology Fee – Project Proposal 2015 Proposal Deadline: Wednesday, January 21, 2015 Project Proposal Type Instructional Technology Enhancement Project (ITEP) Focused projects proposed by an individual or small team with the intention of exploring new applications of instructional technology. ITEPs will typically be led by a faculty “principal investigator.” ITEPs are time-limited projects (up to two years in length) and allocations of Technology Fee funds to these projects are non-recurring. Project Title Crystallography Training Across the Sciences Total Amount of Funding Requested $9,100 Primary Project Coordinator Tim Royappa, Department of Chemistry Crystallography Training Across the Sciences Tim Royappa Department of Chemistry I. Project Description a. Introduction Crystallography has become an indispensable technique in the physical and life sciences. Its im- portance is demonstrated in Table 1, which outlines the chief developments in crystallography since its inception in the early 20th century. In fact, 2014 was designated as the International Year of Crystallography, and the key contributions of crystallography to a wide variety of science disciplines were celebrated across the globe. The reason that crystallography is so important is that it is the best way to elucidate the atomic structure of matter, leading to a better understanding of its physical, chemical and biological properties. Era Discovery/Advance in Crystallography Major Awards Diffraction of X-rays by crystals discovered by Paul Nobel Prize in Physics (1914) Ewald and Max von Laue; von Laue formulates the to von Laue; Nobel Prize in 1910s basics of crystallography; William L. Bragg works out Physics (1915) to Bragg and the fundamental equation of crystallography his father, William H.
    [Show full text]
  • MSE 403: Ceramic Materials
    MSE 403: Ceramic Materials Course description: Processing, characteristics, microstructure and properties of ceramic materials. Number of credits: 3 Course Coordinator: John McCloy Prerequisites by course: MSE 201 Prerequisites by topic: 1. Basic knowledge of thermodynamics. 2. Elementary crystallography and crystal structure. 3. Mechanical behavior of materials. Postrequisites: None Textbooks/other required 1. Carter, C.B. and Norton, M.G. Ceramic Materials Science and Engineering, materials: Springer, 2007. Course objectives: 1. Review of crystallography and crystal structure. 2. Review of structure of atoms, molecules and bonding in ceramics. 3. Discussion on structure of ceramics. 4. Effects of structure on physical properties. 5. Ceramic Phase diagrams. 6. Discussion on defects in ceramics. 7. Introduction to glass. 8. Discussion on processing of ceramics. 9. Introduction to sintering and grain growth. 10. Introduction to mechanical properties of ceramics. 11. Introduction to electrical properties of ceramics. 12. Introduction to bioceramics. 13. Introduction to magnetic ceramics. Topics covered: 1. Introduction to crystal structure and crystallography. 2. Fundamentals of structure of atoms. 3. Structure of ceramics and its influence on properties. 4. Binary and ternary phase diagrams. 5. Point defects in ceramics. 6. Glass and glass-ceramic composites. 7. Ceramics processing and sintering. 8. Mechanical properties of ceramics. 9. Electrical properties of ceramics. 10. Bio-ceramics. 11. Ceramic magnets. Expected student outcomes: 1. Knowledge of crystal structure of ceramics. 2. Knowledge of structure-property relationship in ceramics. 3. Knowledge of the defects in ceramics (Point defects). 4. Knowledge of glass and glass-ceramic composite materials. 5. Introductory knowledge on the processing of bulk ceramics. 6. Applications of ceramic materials in structural, biological and electrical components.
    [Show full text]
  • Materials Science and Engineering 1
    Materials Science and Engineering 1 EN.515.603. Materials Characterization. 3 Credits. MATERIALS SCIENCE AND This course will describe a variety of techniques used to characterize the structure and composition of engineering materials, including metals, ENGINEERING ceramics, polymers, composites, and semiconductors. The emphasis will be on microstructural characterization techniques, including optical The Materials Science and Engineering Program for professionals allows and electron microscopy, x-ray diffraction, and acoustic microscopy. students to take courses that address current and emerging areas Surface analytical techniques, including Auger electron spectroscopy, critical to the development and use of biomaterials, electronic materials, secondary ion mass spectroscopy, x-ray photoelectron spectroscopy, structural materials, nanomaterials and nanotechnology, and related and Rutherford backscattering spectroscopy. Real-world examples of materials processing technologies. Students in this program gain an materials characterization will be presented throughout the course, advanced understanding of foundational concepts and are exposed to including characterization of thin films, surfaces, interfaces, and single the latest research that is driving materials-related advances. crystals. Courses are offered at the Applied Physics Laboratory, the Homewood EN.515.605. Electrical, Optical and Magnetic Properties. 3 Credits. campus, and online. An overview of electrical, optical and magnetic properties arising from the fundamental electronic and atomic structure of materials. Continuum materials properties are developed through examination of microscopic Program Committee processes. Emphasis will be placed on both fundamental principles and James Spicer, Program Chair applications in contemporary materials technologies.Course Note(s): Principal Professional Staff Please note that this 515 course is also listed as a 510 course in the full- JHU Applied Physics Laboratory time program.
    [Show full text]
  • Biological Materials: a Materials Science Approach✩
    JOURNALOFTHEMECHANICALBEHAVIOROFBIOMEDICALMATERIALS ( ) ± available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/jmbbm Review article Biological materials: A materials science approachI Marc A. Meyers∗, Po­Yu Chen, Maria I. Lopez, Yasuaki Seki, Albert Y.M. Lin University of California, San Diego, La Jolla, CA, United States ARTICLEINFO ABSTRACT Article history: The approach used by Materials Science and Engineering is revealing new aspects Received 25 May 2010 in the structure and properties of biological materials. The integration of advanced Received in revised form characterization, mechanical testing, and modeling methods can rationalize heretofore 20 August 2010 unexplained aspects of these structures. As an illustration of the power of this Accepted 22 August 2010 methodology, we apply it to biomineralized shells, avian beaks and feathers, and fish scales. We also present a few selected bioinspired applications: Velcro, an Al2O3­PMMA composite inspired by the abalone shell, and synthetic attachment devices inspired by gecko. ⃝c 2010 Elsevier Ltd. All rights reserved. Contents 1. Introduction and basic components ............................................................................................................................................. 1 2. Hierarchical nature of biological materials ................................................................................................................................... 3 3. Structural biological materials.....................................................................................................................................................
    [Show full text]
  • Basic Crystallography – Data Collection and Processing
    Basic Crystallography – Data collection and processing Louise N. Dawe, PhD Wilfrid Laurier University Department of Chemistry and Biochemistry References and Additional Resources Faculty of Science, Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry. ‘Interpretation of Crystal Structure Determinations’ 2005 Course Notes: http://www.cryst.chem.uu.nl/huub/notesweb.pdf The University of Oklahoma: Chemical Crystallography Lab. Crystallography Notes and Manuals. http://xrayweb.chem.ou.edu/notes/index.html Müller, P. Crystallographic Reviews, 2009, 15(1), 57-83. Müller, Peter. 5.069 Crystal Structure Analysis, Spring 2010. (Massachusetts Institute of Technology: MIT OpenCourseWare), http://ocw.mit.edu/courses/chemistry/5- 069-crystal-structure-analysis-spring-2010/. License: Creative Commons BY-NC-SA X-ray Crystallography Data Collection and Processing • Select and mount the crystal. • Center the crystal to the center of the goniometer circles (instrument maintenance.) • Collect several images; index the diffraction spots; refine the cell parameters; check for higher metric symmetry • Determine data collection strategy; collect data. • Reduce the data by applying background, profile (spot- shape), Lorentz, polarization and scaling corrections. • Determine precise cell parameters. • Collect appropriate information for an absorption correction. (Index the faces of the crystal. A highly redundant set of data is sufficient for an empirical absorption correction.) • Apply an absorption correction to the data. (http://xrayweb.chem.ou.edu/notes/collect.html) Single crystal diffraction of X-rays Principle quantum number n = 1 K level Note: The non SI unit Å is normally used. n = 2 L level 1 Å = 10-10 m n = 3 M level etc… L to K transitions produce 'Ka' emission M to K transitions produce 'Kb' emission.
    [Show full text]
  • Structure Determination by X-Ray Crystallography
    Chem 406: Biophysical Chemistry Lecture 7: Structure Determination by X-ray Crystallography I. Introduction A. Most of the structures in the Protein Data Bank (PDB) were determined by x-ray diffraction. 1. PDB Statistics 2. Other names for x-ray diffraction a. x-ray crystallography b. crystallography B. In the past couple of years there has been a growing number of structures, particularly of small proteins and peptides, that have been solved using a combination nuclear magnetic resonance (NMR) and computational chemistry. 1. PDB Statistics C. The structural information obtained from these techniques are the coordinates of the atoms in the molecule. Overhead 1 (Print out of a PDB file) II. Image magnification A. We will look first at techniques that determine structures by producing images; these include light microscopy, electron microscopy and X-ray crystallography; first, though, we need to look into the properties of light. B. Light 1. The wavelike nature of light (electromagnetic radiation) a. Light waves are depicted as having oscillating electric and magnetic field components that are at right angles to one another. b. These waves are described using the following parameters. Overhead 2 and on board ( a light wave) i. wavelength () ii. frequency ( = c/) iii. Energy (E = h) 1. The constant h, is Planck’s constant and is equal to 6.63 x 10-34 Js (Joule-seconds). 2. Light scattering and refraction a. When light passes through matter the oscillating electrical field polarizes the atoms present in the matter. i. Remember that atoms are made of a nucleus containing positively charged protons and is surrounded by negatively charged electrons.
    [Show full text]
  • Materials Science
    Materials Science Materials Science is an interdisciplinary field combining physics (fundamental laws of nature), chemistry (interactions of atoms) and biology (how life interacts with materials) to elucidate the inherent properties of basic and complex systems. This includes optical (interaction with light), electrical (interaction with charge), magnetic and structural properties of everyday electronics, clothing and architecture. The Materials Science central dogma follows the sequence: Structure—Properties—Design—Performance. This involves relating the nanostructure of a material to its macroscale physical and chemical properties. By understanding and then changing the structure, material scientists can create custom materials with unique properties. The goal of the materials science minor is to create a cross-disciplinary approach to fundamental topics in basic and applied physical sciences. Students will gain experience and perspectives from the disciplines of chemistry, physics and biology. The minor places a strong emphasis on current nanoscale research methods in addition to the basics of electronic, optical and mechanical properties of materials. Any student with an interest in pursuing the cross-disciplinary minor in materials science should consult with the coordinator of the minor. Students are encouraged to declare their participation in their sophomore year but no later than the end of the junior year. Students also should seek an adviser from participating faculty. Degree Requirements for the Minor General College requirements
    [Show full text]
  • Simplified Protein Design Biased for Prebiotic Amino Acids Yields A
    Simplified protein design biased for prebiotic amino acids yields a foldable, halophilic protein Liam M. Longo, Jihun Lee1, and Michael Blaber2 Department of Biomedical Sciences, Florida State University, Tallahassee, FL 32306-4300 Edited by Brian W. Matthews, University of Oregon, Eugene, OR, and approved December 19, 2012 (received for review November 9, 2012) A compendium of different types of abiotic chemical syntheses reducing the potential diversity of interactions that can be encoded identifies a consensus set of 10 “prebiotic” α-amino acids. Before the to that of currently proposed theoretic limits for foldability (14– emergence of biosynthetic pathways, this set is the most plausible 16) (thus, to be able to support protein foldability, the 10 pre- resource for protein formation (i.e., proteogenesis) within the overall biotic amino acids would need to be a remarkably efficient selec- process of abiogenesis. An essential unsolved question regarding tion); (ii) aromatic residues, key contributors to extensive van der this prebiotic set is whether it defines a “foldable set”—that is, does Waals interactions in hydrophobic cores that serve as a driving force it contain sufficient chemical information to permit cooperatively for protein collapse, are absent in the prebiotic alphabet; and (iii) folding polypeptides? If so, what (if any) characteristic properties there are no basic amino acids in the prebiotic set, thus restricting might such polypeptides exhibit? To investigate these questions, protein design to acidic polypeptides, limiting the presence of salt two “primitive” versions of an extant protein fold (the β-trefoil) were bridge interactions and resulting in acidic pI (1, 3). produced by top-down symmetric deconstruction, resulting in a re- To date, there has been no experimental demonstration that the duced alphabet size of 12 or 13 amino acids and a percentage of prebiotic set of amino acids comprises a foldable set; additionally, prebiotic amino acids approaching 80%.
    [Show full text]
  • Geochemistry and Crystallography of Recrystallized Sedimentary Dolomites
    Goldschmidt2019 Abstract Geochemistry and crystallography of recrystallized sedimentary dolomites GEORGINA LUKOCZKI1*, PANKAJ SARIN2, JAY M. GREGG1, CÉDRIC M. JOHN3 1 Oklahoma State University, Boone Pickens School of Geology, Stillwater, OK, USA 2 Oklahoma State University, School of Materials Science and Engineering, Tulsa, OK, USA 3 Imperial College London, Department of Earth Science and Engineering, London, UK (*Correspondence: [email protected]) Most sedimentary dolomites [CaMg(CO3)2] are meta- stable upon formation and either transform into more stable dolomite via recrystallization, or persist as meta-stable phases over deep geological time. The stability of dolomite has long been considered to be influenced by ordering and stoichiometry [1]; however, how recrystallization alters the crystal structure and chemistry of dolomites remains poorly understood. In order to better understand the relationship between various chemical and crystallographic properties and the underlying geological processes, sedimentary dolomites, formed in various diagenetic environments, were investigated in detail. The innovative aspect of this study is the application of high resolution diffraction techniques, such as sychrotron X-ray and neutron diffraction, together with various geochemical proxies, including clumped isotopes, to characterize recrystallized sedimentary dolomites. The age of the studied samples ranges from Holocene to Cambrian. The diagenetic environments of dolomitization and recrystallization were determined primarily on the basis of petrographic and geochemical data [2, 3, 4]. Rietveld refinement of high-resolution diffraction data revealed notable differences in crystallographic parameters across the various dolomite types. Several dolomite bodies have been identified as potential sites for CO2 sequestration [5]; therefore, new insights into what factors control dolomite ordering and stoichiometry will contribute to an improved understanding of dolomite reactivity and may be particularly important for CO2 sequestration studies.
    [Show full text]
  • Glossary of Materials Engineering Terminology
    Glossary of Materials Engineering Terminology Adapted from: Callister, W. D.; Rethwisch, D. G. Materials Science and Engineering: An Introduction, 8th ed.; John Wiley & Sons, Inc.: Hoboken, NJ, 2010. McCrum, N. G.; Buckley, C. P.; Bucknall, C. B. Principles of Polymer Engineering, 2nd ed.; Oxford University Press: New York, NY, 1997. Brittle fracture: fracture that occurs by rapid crack formation and propagation through the material, without any appreciable deformation prior to failure. Crazing: a common response of plastics to an applied load, typically involving the formation of an opaque banded region within transparent plastic; at the microscale, the craze region is a collection of nanoscale, stress-induced voids and load-bearing fibrils within the material’s structure; craze regions commonly occur at or near a propagating crack in the material. Ductile fracture: a mode of material failure that is accompanied by extensive permanent deformation of the material. Ductility: a measure of a material’s ability to undergo appreciable permanent deformation before fracture; ductile materials (including many metals and plastics) typically display a greater amount of strain or total elongation before fracture compared to non-ductile materials (such as most ceramics). Elastic modulus: a measure of a material’s stiffness; quantified as a ratio of stress to strain prior to the yield point and reported in units of Pascals (Pa); for a material deformed in tension, this is referred to as a Young’s modulus. Engineering strain: the change in gauge length of a specimen in the direction of the applied load divided by its original gauge length; strain is typically unit-less and frequently reported as a percentage.
    [Show full text]
  • Crystallography and Chemistry: an Ongoing Engagement Gautam R
    Angewandte. Editorial DOI: 10.1002/anie.201308513 Crystallography and Chemistry: An Ongoing Engagement Gautam R. Desiraju* Crystallography is as old as chemistry therefore sufficient unto itself. It has no itself. As an intellectual endeavour, it is practical influence in a living context for practically without equal, such that its most precious products, crystalline however, crystallography was derided as Johann Wolfgang von Goethe, who was gems, first have to be cut and polished a “tool” of no research significance, and also interested in mineralogy, said al- before we can use them to adorn our organic chemists, mostly between 1960 womenfolk.” In contrast, his attitude to and 1990, would often ask rhetorically as chemistry is more generous as he states to the relevance of the structure of “The opposite can be said of chemistry, a molecule in the crystal in the context which can be applied in the most of its solution chemistry. Much of this extensive way and proves to be of the mercifully came to an end with the most unlimited influence on life.”[**] advent of organometallic chemistry The contrast between crystal statics and the appearance of a large number and chemical dynamics continues to of compounds whose complex internal pervade and persist in the consciousness molecular structures could not be deter- of chemists, even though crystallogra- mined in solution; notably NMR spec- phy and chemistry have merged in many troscopy was not an effective structure- most regretfully, if a little disparagingly contexts and are almost indistinguish- determining “tool” for this category of “Seen as a science, crystallography is an able today.
    [Show full text]