Chemical Education Today
Book & Media Reviews
Crystal Structures: Lattices and Solids in Stereoview by Mark Ladd Horwood: Chichester, UK, 1999. xiii + 171 pp. Figs., tables, charts. 17.5 × 24.5 cm. ISBN 1-898563-2. $45.00. reviewed by Guy Crundwell
By title and cover design, Crystal Structures: Lattices and Solids in Stereoview appears to be a crystallography text. The preface further fortifies this belief by briefly describing the content of the book. The author wishes to introduce undergraduate students to a variety of crystal structures using a stereoviewer. At the same time, he hopes to introduce the fundamental elements of crystallography such as point-group symmetry, unit cells, Bravais lattices, and space groups. In essence, this unique book combines approaches encountered in traditional crystallography, descriptive solid-state chemistry, and physical chemistry texts. (This is not surprising, because Ladd has previously written books in all three fields.) This text is best suited for those teaching upper-level solidstate chemistry courses who wish to downplay the experimental aspect of crystal structure determination. The book consists of six chapters, the first of which introduces students to the construction and use of a stereoviewer. The author’s intention in using a stereoviewer is to illustrate the three-dimensional symmetry of crystal lattices. Unfortunately, instead of providing a stereoviewer, the book describes how a student can make one from scratch. While I do not doubt that lenses for stereoviewers are commercially available (a stereoviewer merchant in New York is suggested), I would guess that most students would not put in the extra effort during the semester to construct their own stereoviewer. (One can view the images adequately without a stereoviewer by relaxing one’s eyes; but doing so repeatedly for hours produces a headache.) My initial reaction to the use of stereoviews as a teaching aid was: Why didn’t the author choose to add a supplemental CD containing crystal structure files for computer-based molecular visualization? However, after I borrowed the stereoviewer from another text I understand completely why the author chose this approach. First, you do not need a computer. Second, the orientations of the stereoviews are well chosen and are excellent at pointing out the three-dimensional aspects of crystal symmetry. The first chapter also introduces students to symmetry operations, point groups, lattices, and space groups. Unfortunately, the portion dedicated to point groups was the weakest section of the text. The author starts out describing only three symmetry operations (rotation, reflection, and roto-inversion) and then moves directly to reference axes in crystals. From this foundation, he moves to a discussion of point groups. In this section, before any explanatory text, he unleashes two tables introducing the Bravais lattices, their crystallographic point groups (with and without centers of inversion), and their
edited by
Jeffrey Kovac University of Tennessee Knoxville, TN 37996-1600
characteristic symmetries along crystallographic directions of interest. I believe students will find these two tables incredibly daunting because they are laden with terminology not yet covered (e.g., the third position in the point group 6/mmm corresponds to a 2¯ along ). Pedagogically, I find the author’s use of lattices as examples to illustrate the various point group symmetries interesting; but once again, the section could have been better organized and written. Despite the problems with the point group section, the rest of this chapter is absolutely excellent. The author introduces Bravais lattices, centering options, and lattice transformations with perfect clarity—aided by copious stereoviews that clearly illustrate his points. The chapter ends with a sound treatment of space groups that nicely explains the wealth of information students can acquire from The International Tables for Crystallography Volume A. Chapters 2–5 introduce ionic, covalent, metallic, and molecular structures, respectively. They constitute the body of the text and are well written. These chapters have similar layouts. Initially, the author addresses the forces that bind each of these types of solids: Coulombic attraction between ions, wave mechanics of covalent bonds, density of states, and dipole– dipole interaction. He treats each subject thoroughly, giving complete mathematical workups and providing several examples. After introducing the mathematical background, he provides many descriptive sections peppered with beautiful stereoviews. Throughout the text, he addresses all the vital components of a solid-state chemistry course. Below are a few examples of what the reader will find. Chapter 2: Looking at Ionic Structures. Lattice energies, radius ratio rules, thermodynamic aspects of solubility. Chapter 3: Looking at Covalent Structures. Electron-in-abox, linear combination of atomic orbitals, molecular orbital theory, ionic–covalent character in bonds. Chapter 4: Looking at Metallic Structures. Free-electron theory of metals, Fermi–Dirac equation, band theory, HumeRothery’s rules for alloy systems, semiconductors. Chapter 5: Looking at Molecular Structures. Intermolecular potentials, packing of molecules, disorder. Chapter 5 makes this book unique. Chapters 2 through 4 cover structure types commonly encountered in descriptive inorganic and solid-state chemistry texts (e.g. ionic salts of type MX and MX2, perovskites, spinels, diamond, simple metals). After introducing potential energy calculations of dipole–dipole interactions, the fifth chapter surveys a variety of elemental and organic solids. The latter group is introduced in two sections. The first section describes one example from each of the following structure types: electron overlap, chargetransfer, and clathrates. The second organic section is more substantive and illustrates the effects of molecule size and polarity on crystal packing. The author divides molecules into three categories: spherical, flat, and long. In each category, he introduces a few examples of polar and nonpolar molecules. Both organic sections could have contained more examples to illustrate the variety of ways in which organic molecules pack. Furthermore,
JChemEd.chem.wisc.edu • Vol. 77 No. 12 December 2000 • Journal of Chemical Education
1563
Chemical Education Today
Book & Media Reviews the entire treatment of organic molecules in this section would have been stronger if the author first categorized his choices by the polar nature of the molecules. The classification based on “long” or “flat” seems somewhat arbitrary, especially when anthracene is classified as the former! The final chapter addresses problem solving using several DOS executable files available for download from the publisher’s Internet site. The DOS executables cover a variety of topics (linear regression, calculation of the Madelung constant, electron-in-a-box, etc.) and are relatively unimpressive. For example, there is a point-group recognition program that “has been devised to assist in a study of the point-group symmetry of crystals and molecules”. Before embarking on their computerassisted journey, students have to know the model number(s) the author assigned to the point group. This information is
1564
given in the first appendix (e.g. for point group mm2, the possible model numbers are 16, 64, 71, 76). This process seems more cumbersome than the traditional text flowchart. In summary, two chapters (1 and 6) weaken this otherwise unique introductory solid-state text. The mathematical treatment of the physical phenomena leading to solid formation throughout the text is excellent, and the descriptive sections are well written and cover a plethora of structure types. I would recommend using this textbook in conjunction with other texts and journal articles when teaching a course in solid-state chemistry to upper-level chemistry majors. Guy Crundwell is in the Department of Chemistry, Central Connecticut State University, New Britain, CT 06050;
[email protected].
Journal of Chemical Education • Vol. 77 No. 12 December 2000 • JChemEd.chem.wisc.edu
