Physical properties of diamond

BOOK REVIEWS Melting and Crystal Structure by A. R. Ubbelohde (Clarendon Press, 1965) 325 pages. 63s. T u I s book stands as a healthy corrective to any of us who may be tempted to believe that the major features of the behaviour of bulk matter are reasonably understood. Melting is evidently such a major feature. In simple cases it involves an entropy increase of the order of 2 or 3 calories deg-' mole -1 and a volume increase of about 10 per cent. A rational explanation of these basic facts will not be found in this book nor--presumably--anywhere else. What will be found is a fascinating collection of empirical information about melting ranging from simple facts like those mentioned above to complex facts about complicated substances such as the increase in viscosity at the clearing point of the liquid crystal p-azoxyanisole with some added phenanthrene. The unifying themes of this very dispersed book are: the idea that melting phenomena should be associated with certain mechanisms for increasing entropy (positional, rotational, and configurational); that some of these mechanisms may operate at a temperature below the fusion temperature; that the structure of the liquid is a major key to the understanding of melting. Thus we find important sections on solid-solid transformations involving positional randomization (e.g. Agl, CuZn) and rotational randomization (e.g. CH4) (which might otherwise be thought out of place) and major chapters on structural melting, the melting of flexible molecules, the nature of ionic melts, premelting, and pre-freezing. As is perhaps inevitable, parts of this book are more like an annotated bibliography than a critical survey. Parts of it are indeed uncritical. For example, in discussing the Simon melting equation, dp/d T = c(p + a)/T

(which implies that AHf = c(p + a)AVf) the author says: 'The physical interpretation . . . involves the fraction f of the latent heat which goes to expand the solid on melting. If the work of expansion Wr on fusion is written (U is the internal energy) Wf = f A H f = [p - (bU/bV)r]AVr

comparison . . . shows that c = l/f, and a =

-

(~U/~V)~,

which is approximately the same as a =

-

(~ v / ~ V ) o

for the solid at 0 ° K.' There is no further explanation or comment on this mystifying 'derivation' or its baffling conclusion. Unfortunately this sort of incompleteness is not uncommon. Also, there are many minor CRYOGENICS

• AUGUST

1966

mistakes and omissions, e.g. no ordinate scale is provided for the (quantitative) graph on p. 51 ; there is a mistake in Hall coefficient on p. 181; the statement on p. 43 that the entropy of the liquid is greater than the entropy of the solid for all known substances ignores helium-3, concerning which data---excessive data--are given on p. 39. In spite of these blemishes, we should be grateful to Professor Ubbelohde for his stimulating comments and his 'handy guide' to an extensive and complex literature. It would have been useful to have provided an index to cited authors. The subject index is adequate. R. O. DAVIES Physical Properties of Diamond. Edited by R. Berman (Oxford University Press, 1965) 443 pages. 75s. A s g result of the investigations in several laboratories in co-operation with the diamond industry, a detailed knowledge of the different properties of diamonds has accumulated. Most of this work has been verbally reported in several annual Diamond Conferences held over the past years. The reviewer had the privilege of attending a few of them and one always felt the need for a collected account of the material which has been published in different journals. The appearance of this book is, therefore, to be welcomed. This increase of our knowledge on diamond has contributed to the advances in the general theory of solids which are currently taking place. The book, therefore, is a discussion of the different observed properties of diamond in the light of modern theory of solids. It has been written by a number of scientists and consists of fifteen chapters. Each chapter is a review of a particular aspect of diamond and is selfcontained. The chapters on 'Optical Studies', 'X-ray Diffraction Studies', and some related topics, 'X-ray Topography', 'Ring Cracks', 'Deformation Friction and Wear', 'Transmission Electron Microscopy', 'The Hardness and Wear of Diamond during Grinding and Polishing' are profusely illustrated and contain several beautiful and striking photographs. It is a very well written book and includes chapters on 'Electronic Structure of Diamond', 'Paramagnetic Resonance in Diamond', 'Optical Properties of Natural Diamonds', 'Semiconducting Diamonds', 'Counting Properties of Diamond under Ionizing Radiations' ,'Thermal Properties,' and 'Radiation Damage in Diamond'. Because of the wide range of the investigations, the book will be of interest to solid state scientists and is a welcome addition to the existing literature. A . R . VERMA 245