J. MATER. CHEM., 1994, 4( S), 777-779 BOOK REVIEWS Liquid Crystals. By S. Chandrasekhar. Cambridge University Press. 1992. Second Edition. Pp. xvi +460. Price f22.95. ISBN 0-521 -41 747 3 (Hardback); 0-521 -42741 -X (Softback). Those familiar with the first edition of Professor Chandrasekhar’s ‘Liquid Crystals’ published in 1977 will welcome the appearance of this second edition, which has been considerably extended by the addition of around a further 100 pages of text, and doubling the references to more than 900. For newcomers to the fascinating field of liquid crystals, the book provides a reasonably complete overview of the physics of thermotropic low-molecular-weight liquid crystals. When the first edition appeared in 1977, the subject matter was largely of academic interest, and applications were restricted to simple calculators and watches.Indeed at that time there was considerable discussion amongst experts about which type of display technology (liquid crystal or non-liquid crystal) would be successful in challenging the existing display technologies. Nowadays the widespread availability of liquid crystal watches, calculators, digital indicators, computer screens and increasingly TVs, means that all scientists and most of the general public, will at least have heard of liquid crystals. The success of liquid-crystal science in the area of displays can be attributed in large measure to the development of suitable materials, so it is entirely appropriate to review this new edition in a journal devoted to materials chemistry.To set the subject matter of the book in context, it is important to note that liquid-crystal science is concerned with the study of a wide range of materials, including lyotropic liquid crystals formed by solution of amphiphilic molecules in suitable solvents (usually water), biological membranes, main- and side-chain liquid crystal polymers and thermotropic low-molecular weight liquid crystals which form when certain solid crystals melt. This book is largely concerned with the physics of thermotropic liquid crystals, although lyotropics and polymer liquid crystals do get a very brief mention. It has to be admitted that chemists and materials scientists lacking a good physics base will have a hard time assimilating the contents but the effort will be rewarded with a thorough understanding of the principles of liquid-crystal science.The study of liquid crystals is accurately described as interdisciplin-ary, involving scientists from many backgrounds, and the preparation of a monograph addressed to all should address this diversity in readership. Chandrasekhar attempted to do this in the first edition by ‘presentCing] as far as possible a self-contained treatment of ... different aspects of the subject’, and this approach is perpetuated in the second edition. Thus this is less of a textbook but more of a source book on the physical behaviour of liquid crystals, a point reinforced by the extensive referencing of each of the six chapters. Although wide-ranging in the topics covered, there has, of necessity, been some selection, which reflects to an extent the particular interests of Professor Chandrasekhar and the research group at Bangalore over the years.What is remarkable is the number of areas of liquid crystal studies that the scientists from Bangalore have contributed to, and there are very few topics that do not get a mention. This 400+ page book begins with a brief introductory chapter describing the different structural types of liquid crystals; many of the more recently discovered structural developments, including the polymorphism of smectic A and C liquid crystals, and columnar and discotic liquid crystals are covered in later chapters. Chapter 2 gives a clear account of the statistical theories of nematics, while the third chapter contains an extensive discussion of both static and dynamical aspects of continuum theory, with descriptions of a variety of electric-field effects, including the more esoteric topics of electro-hydrodynamics, flexoelectricity and order electricity.Chapter 4 entitled ‘Cholesteric liquid crystals’, contains a useful introduction to the optics of twisted structures using Jones matrices, and a brief mention of the doubly twisted cubic phases known generically as blue phases. The essential feature of these, and indeed other twisted smectic and colum- nar phases is their intrinsic chirality-the relationship to derivatives of cholesterol is more and more tenuous, and hopefully the old classification of ‘cholesteric liquid crystals’ will soon vanish.The chapter on smectic liquid crystals has been considerably extended from the first edition and now contains details of modulated smectic A and smectic C phases as well as the twisted chiral smectic A (twist grain boundary) phase and the chiral ferroelectric smectic C phase. which is the basis of a new generation of fast-switched ferroelectric liquid crystal displays. Since Professor Chandrasekhar and his group art: credited with the discovery in 1977 of a new category of thermotropic liquid crystals based on disc-shaped molecules, it is fitting that the new and final chapter of ‘Liquid Crystals’ should be devoted to discotic liquid crystals.This includes details of structural types of discotic liquid crystals as well as their theory and a description of the defects observed. Perhaps it is worth noting that throughout this book the fluid-state defects and disclinations characteristic of all liquid crystalline phases are discussed in some detail, and this provides a recurring theme through the text. Intermediate in structure between the nematic phases of rod-like (long-axes ordered) and disc-like molecules (short-axes ordered) is the biaxial nematic in which both long and short molecular axes are ordered, and the final section of the book is devoted to a description of such a phase. It must be said that the existence of a low-molecular-weight thermotropic biaxial nematic is still the subject of controversy, but the structural basis for the phase is clear enough.The selection of topics means that there are a few subjects that get little or no attention. For example hexatic phases (smectics B, F and I) have a very brief mention, while there is little on device physics, liquid crystalline materials for applications and the relationships between molecular proper- ties and liquid crystalline behaviour. This is in no sense a criticism, and it is remarkable how many aspects of liquid- crystal science are dealt with in this book. The second edition of Chandrasekhar’s ‘Liquid Crystals’ can be recommtmded to any liquid crystal scientist wishing to have a comprehensive account of the physics of liquid crystals. D.Dunmur Receioed 13th January, 1994 Photochemical Vapour Deposition. By J. G. Eden. Volume 122 in Chemical Analysis: A Series of Monographs on Analytical Chemistry and Its Applications. Wiley-lnterscience, 1992. Pp. xi +194.Price f43.95.ISBN 0-471 -55083-3. Chemical vapour deposition (CVD) represents a well-established technology for the successful production of thin films for a variety of advanced materials applications, all of which rely on the ability of the technique to deposit films of controllable composition and uniform thickness. Photochemical vapour deposition is a more recent develop- ment of CVD in which the rate and products of deposition are influenced by the presence of light. The introduction of visible, ultraviolet or vacuum ultraviolet photons to a CVD reactor offers new possibilities in respect of (i) the production of novel materials and (ii) overcoming some of the short- comings associated with conventional CVD, in particular the requirement for high growth temperatures and consequent less than ideal selectivity of deposition.As stated in the preface the purpose of this book is to provide an overview of photochemical vapour deposition with the following audiences in mind: the student approaching photodeposition for the first time, the thin-film engineer wishing to evaluate photochemical vapour deposition for a particular application and possibly to adapt it to an existing process, and the experienced researcher desiring a review of the work completed to date.Meeting these diverse require- ments within a single volume would appear to be a rather daunting task, but since the field of photochemical vapour deposition is still young the author has been able to achieve this satisfactorily with a timely book which is organized in the following manner. The first three chapters comprise intro- ductory material describing the basic principles underlying photochemical vapour deposition and practical aspects of designing appropriate reactor systems, with particular em-phasis on the choice (and limitations) of optical sources. Subsequent chapters include detailed discussions of the current status of the technique with respect to the growth of metal (Chapter 4, 26 pp.), semiconductor (Chapter 5, 45 pp.) and dielectric (Chapter 6, 19 pp.) films.Other applications such as the growth of metal oxide films constituting the high T, superconductor compositions and light-enhanced surface pro- cessing such as cleaning and nitridation are briefly covered. The concluding chapter provides an assessment of the future prospects for photochemical vapour deposition. As indicated above, the emphasis of the contents of the book concerns the versatility of the technique for growing metal, semiconductor and dielectric films. Applications receiv- ing special attention include the photodeposition of dielectric films for the fabrication of VLSI devices and the growth of amorphous hydrogenated silicon for photovoltaic appli-cations. These aspects are comprehensively covered and, in many cases, comparisons are provided with the results from other more well-established deposition routes, e.g.plasma CVD, MOCVD, MBE etc. The coverage includes much tabulated information that will serve as an excellent source of reference for both academic and industrial scientists from a range of disciplines including chemistry, physics, electronics, electrical engineering and materials science. The advantages offered by photochemical vapour deposition clearly lie in the lower processing temperature requirement, which frequently results in enhanced selectivity of deposition and lower levels of contaminants in the resultant films; particularly, the bane of conventional CVD, adventitious carbon. In view of the recent MOCVD studies in which preformed adducts of parent precursors have been successfully used to provide some ‘tailor- ing’ of the behaviour of the parent during the decomposition process it is perhaps surprising that this does not yet appear to have been used in tandem with photochemical vapour deposition.The book has been written by an active and expert prac- titioner of the subject in a clear and easy to read style. It contains few typographical errors and is well referenced. However, the index is barely adequate. As with any rapidly advancing field the obvious danger lies in the fact that the book will rapidly become out of date. Nevertheless, it provides both an excellent ‘state of the art’ view of the field in the early 1990s and a very good reference source of the subject area.Although a variety of films have been grown successfully by conventional CVD processes, the author acknowledges that the development of photochemical vapour deposition as a J. MATER. CHEM., 1994, VOL. 4 reliable tool for the device engineer or the materials scientist is still in its infancy. Indeed, in terms of applications and understanding, photochemical vapour deposition probably occupies a similar position to CVD 10-15 years ago. Much remains to be discovered and understood. Hopefully, the specific advantages that are highlighted in this book will focus the attention of device engineers and materials scientists and enhance the general awareness of the technique. R.Whyman Receiued 7th January, 1994 Superconductivity Today (An Elementary Introduction).By T. V. Ramakrishnan and C. N. R. Rao. Wiley Eastern. 1992. Pp. x +116. Price Rs 55.00. ISBN 81-224-0391-3. ~~~~~ This slim volume is intended as an elementary introduction to the field of superconductivity, mainly for graduate and postgraduate students. Written in a readable way, it encompasses historical perspectives and a phenomenological description of superconductivity, together with an account of superconducting materials. The book also includes a chapter containing convenient ‘potted’ accounts of the development of theories of superconductivity up to 1956, including the London equation, Ginsburg-Landau and BCS theories. A separate chapter is devoted to the anomalous properties of cuprates, together with descriptions of recent theories put forward to explain their normal state and superconducting properties.As a chemist, I found the two chapters describing theories to be particularly useful and well written; both are presented at a very accessible level for graduate or postgradu- ate students, and while not especially rigorous, they give a good flavour of the basic ideas behind the different theoretical developments. The book concludes with short sections on applications of superconductivity, and the challenges still before us. In this rapidly developing area, any text-book runs the risk of becoming out-of-date before publication; casualties here are the doped C60 superconductors (mentioned only in a footnote in the materials chapter, and briefly in the final section), and the Hg-containing cuprates.The description of superconducting materials as a whole is probably one of the less impressive parts of the book; it contains adequate descrip- tions of a range of superconducting materials from conven- tional alloys to cuprates (but very little on organic CT compounds), but the discussion of the features of a structure which are important for superconducting behaviour is not well developed. I suspect these parts of the book would leave a rather confused impression in the mind of a student not already familiar with the materials discussed. Since 1987, I have been looking for a short introductory text that I can recommend to 3rd year undergraduates and 1st year postgraduates in chemistry, in order to give them a concise overview of superconductivity without swamping them in formulae.This book is by no means perfect in this respect since, in order to be concise, much is glossed over, and there are a few points where the text does not flow well as a result. There are a number of typographical errors in formulae and some errors in the text (for example the description of the Jahn-Teller distortion of the CuO, octahedra in the cuprates). Nevertheless, the book is very accessible and covers a wide range of topics in an interesting and stimulating way. It will certainly be useful to any student, and given the nature of the subject matter, perhaps no authors could hope for more.The book appears to be written to some extent for the Tndian market (for example, the final section comments specifically J. MATER. CHEM., 1994, VOL. 4 on the challenges facing the Indian scientific community) and is priced very attractively at Rs 55.00. Whatever the price on the wider market, the book is probably worth the cover price for the concise, palatable theory chapters alone. W. Flavell Received 7th January, 1994 Solid State Chemistry: Compounds. Ed. A. K. Cheetham and P. Day. Clarendon Press, Oxford, 1992. Price €40.00. Pp. xii +304. ISBN 0-19-855166-5. This is a multi-author companion to Solid State Chemistry: Techniques published in 1988 and the new volume is a valuable addition to the literature devoted to solid state chemistry.The one disappointment attaching to it is that, while the title implies a general coverage of the subject, the reader discovers that the book deals with selective topics only. However, the topics included have been well chosen, covering electronic structure as an essential starting point followed by treatments of several classes of materials that have been prominent in solid state chemical chemistry research in recent years. In the preface the editors express the hope that they will be able to deal with optoelectronic materials, magnetic materials and solid electrolytes in a further volume. The material is presented lucidly by a distinguished team of contributors and the editors have achieved an effective structure that results in a ‘good read’.The classes of materials included are: chain compounds, superconducting materials (inorganic only), metal-rich compounds, heterogeneous cata- lysts, intercalated layered compounds, zeolites and ferroics (a generic grouping including ferro-magnetic, ferro-electric and ferro-elastic materials). There are no weak chapters and the surveys of superconducting materials, metal-rich compounds and intercalation in layered compounds are particularly useful. The volume is well referenced and well indexed. It should prove useful for final year undergraduates studying special topics and for first year graduate students embarking on research in the field. P. T. Moseley Received 23rd December, 1993 Fatigue of Materials.By S. Suresh. Cambridge Solid State Science Series. Cambridge University Press, 1992. Pp. xviii +618. Price €24.95,ISBN 0-521-43763-6. As the author clearly states, the fatigue behaviour of load- bearing materials is of utmost concern in a wide range of engineering applications. In spite of this, very few complete and well-balanced text-books are presently available on the market. ‘Fatigue of Materials’ certainly goes a long way to resolving this problem. The book presents a comprehensive treatment covering both the physics as well as the mechanics of crack initiation and propagation in materials as diverse as ductile metals, brittle ceramics and high performance com-posite materials. The author refers to almost 1000 scientific articles covering virtually all aspects of the fatigue behaviour of modern materials.The book begins with an interesting review of’ the early pioneering work undertaken in the late nineteenth and early twentieth century. The introduction continues by presenting the different approaches that are currently adopted in acade- mia and industry for characterizing the long-term behaviour of structures and components. The early chapters consider the problem of deformation and fatigue crack initiation in a range of ductile materials. Here, the influence of grain boundaries in metals, cyclic hardening in polycrystals and other relevant effecr s are dis- cussed in terms of microstructural and environmental aspects. Following this, a short chapter examining phenomenological continuum approaches for characterizing the total fatigue life of a material is presented.Chapter 5 outlines the principles of fracture mechanics and their application to fatigue loading. Here, one feels that the chapter is perhaps misplaced since it somewhat breaks the rhythm between the chapters on fatigue crack initiation in ductile solids and on fatigue crack growth inductile solids. Perhaps this section would have been better placed in an earlier chapter. The subsequent chapters consider fundamental subjects, such as stress concentrations, small fatigue cracks and variable amplitude fatigue loading. Chapter 12 contains a well written introduction to environ- mental effects covering corrosion cracking and high tempera- ture fatigue response in an interesting and detailed manner. The later chapters present the problem of fatigue of brittle, semicrystalline and non-crystalline solids. In these sections considerable attention is given to failure in ceramics as well as polymeric materials. The final chapter outlines ~t number of fascinating (although sometimes fatal) case studies. Here, many of the concepts presented in earlier chapters are re-discussed putting them very much in an application-minded context. The book also contains a significant number of problems suitable for undergraduates as well as postgraduates. Without doubt, ‘Fatigue of Materials’ represents an invalu-able addition to an engineers or researchers library. Certain chapters would be well suited to postgraduate courses in either materials science or mechanical engineering. It IS written in a style that is both clear and easy to read. The figures are well presented and pertinent. The relatively low price of E25 makes it excellent value for money! W. J. Cantwell Received 17th Febru,zry, 1994