Symmetry, Group Theory, and the Physical Properties of Crystals

ISBN-13: 9781441975973 / Angielski / Miękka / 2010 / 244 str.

Richard C. Powell

Opis

Whydowelookatsomethingsandthinktheyarebeautifulwhileotherthingsdo notappearestheticallypleasingtous?Thisisaquestionthathasalwaysinterested mankind. Oneanswerisgivenbythefollowingquotationfromanearlypresidentof theCollegeofNewJersey(nowPrincetonUniversity): "Beautyisfoundinimmaterialthingslikeproportionoruniformity. . . . calledbyvariousnamesofregularity, order, uniformity, symmetry, 1 proportion, harmony, etc. ." . . JonathanEdwards Symmetrynotonlyprovidesthenaturalharmonythatmakessomethingappear beautifultous, butalsoisofgreatvaluetosciencebecauseitdictatesthephysical traitsofmanyobjects. Natureitselfseemstolovebeautysinceatomstendtoself? assemble into shapes with speci?c symmetry and crystals grow in geometric lattices. Inmanycases, ifweknowthesymmetryofsomethingwecanpredict someofitsimportantpropertieswithouthavingtoresorttoexperimentationor complicatedcalculations. One area where the concept of symmetry plays an important role is that of crystalline solids. Crystals, by their very nature, exhibit speci?c symmetries. Crystallinematerialshavemanyimportantapplicationsindevicesbasedontheir electronic, optical, thermal, magnetic, andmechanicalproperties. Solidstatep- sicistsandchemists, aswellasmaterialscientistsandengineers, havedeveloped rigorousquantumtheoreticalmodelstodescribethesepropertiesandsophisticated measurementtechniquestoverifythesemodels. Manytimes, however, inscreeningmaterialsforanewapplicationitisuseful to be able to quickly and easily determine if a speci?c material will have the appropriatepropertieswithoutmakingdetailedcalculationsorexperiments. This canbedonebyanalyzingthesymmetrypropertiesofthematerial. Themathema- calformalismthathasbeendevelopedtoaccomplishthisiscalledgrouptheory. Thesymmetrypropertiesofacrystalcanbedescribedbyagroupofmathematical 1 J. Edwards, WorksofJonathanEdwards(BannerofTruthTrust, Edinburgh,1979) v vi Preface operations. Thenusingsimplegrouptheoryprocedures, thephysicalpropertiesof thecrystalcanbedetermined. Duringthe45yearsIhavebeeninvolvedinteachingandresearchinvarious areasofsolidstatephysics, Ihavemadeextensiveuseoftheconceptsofgroup theory. YetIhavebeensurprisedathowlittleemphasisthistopicreceivesinany formaleducationalcurriculum. Generally, astudentstudyingsolidstatephysicsor chemistrywillbeexposedtocrystalstructuresearlyinthesemesterandthenhave nofurtherexposuretocrystalsymmetryuntilsomespecialtopicsuchasnonlinear opticsisdiscussed. Thisbookfocusesonthesymmetryofcrystalsandthedescr- tionofthissymmetrythroughtheuseofgrouptheory. Althoughspeci?cexamples are provided of using this formalism to determine both the microscopic and macroscopicpropertiesofmaterials, theemphasisisonthecomprehensive, per- sivenatureofsymmetryinallareasofsolidstatescience. Theintentofthebookistobeareferencesourceforthosedoingresearchor teachinginsolidstatescienceandengineering, oratextforaspecialtycoursein grouptheoryappliedtothepropertiesofcrystals. Tucson, AZ RichardC. Powell June2010 Contents 1 SymmetryinSolids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 1 Symmetry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 2 CrystalStructures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. 3 SymmetryinReciprocalSpace. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1. 4 Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Spis treści

Symmetry in Solids.- Group Theory.- Tensor Properties of Crystals.- Symmetry Properties of Point Defects in Solids.- Symmetry and the Optical Properties of Crystals.- Nonlinear Optics.- Symmetry and Lattice Vibrations.- Symmetry and Electron Energy Levels.

O autorze

I. Symmetry in Solids II. Group Theory III. Tensor Properties of Crystals IV. Symmetry Properties of Point Defects in Solids V. Symmetry and the Optical Properties of Solids VI. Nonlinear Optics VII. Symmetry and Lattice Vibrations VIII. Symmetry and Electron Energy Levels

Blurb

This book demonstrates the importance of symmetry in determining the properties of solids and the power of using group theory and tensor algebra to elucidate these properties. It provides the fundamentals necessary for the reader to understand how to utilize these techniques in many different applications without becoming lost in a heavy formal treatment of the subject matter. The book begins by discussing the concepts of symmetry relevant to crystal structures. This is followed by a summary of the basics of group theory and how it applies to quantum mechanics. Next is a discussion of the description of the macroscopic properties of crystals by tensors and how symmetry determines the form of these tensors. The basic concepts covered in these early chapters are then applied to a series of different examples including crystal field theory treatment of point defects in solids, molecular orbitals, two-photon processes, the optical properties of solids, the nonlinear optical properties of solids, lattice vibrations, the Jahn-Teller effect, and the effects of translational symmetry on electronic energy bands in solids.. Emphasis is placed on showing how group theory and tensor algebra can provide important information about the properties of a system without resorting to first principal quantum mechanical calculations. The book also features a comprehensive set of relevant tables, including crystal symmetries, point group character tables, matter tensors of different rank, and other tensor properties. Key Features: •Serves as a textbook or reference book for solid-state physics, solid-state chemistry, and materials science and engineering •Shows how the physical properties of solids are determined by their symmetry •Demonstrates the applications of group theory •Utilizes the concept of matter tensors •Includes an extensive set of reference tables and end of chapter problems