N. Mott and R. Gurney, Electronic Processes in Ionic Crystals, translated under the editorship of and with a foreword by Academician A. F. Ioffe. Foreign Literature Publishing House, Moscow, 1950. Price 18 rubles 10 kopecks.

In Russian and foreign literature, the theory of metals occupies considerably more space than the theory of nonmetallic crystals. This state of affairs by no means corresponds to the relative importance that nonmetallic crystals have in nature and in technology.

The most diverse branches of technology and sections of physics are based, in the final analysis, on the theory of nonmetallic solids.

Bibliography

Questions of electrical insulation, the phenomenon of dielectric breakdown, the mechanism of formation of a photographic image, the electrical properties of semiconductors, in particular their rectifying properties used in technology, lead us to the general theory of the solid state. The mechanism of processes occurring in crystal phosphors under the action of illumination can also be understood only on the basis of the modern theory of the solid state. Finally, the theory of the solid state is of interest for physical chemistry, which studies adsorption and heterogeneous catalysis, for without it one cannot understand the chemical processes developing on the surface of a solid body (metal or nonmetal). All these diverse phenomena are ultimately conditioned by electronic processes occurring inside the crystal or on its surface, and they represent various aspects of the same electronic mechanisms. It is regrettable that, despite the wealth of experimental material and the abundance of varied theoretical work, there has until now been no book in which all these phenomena would be considered from a single point of view and in which their electronic mechanism would be revealed.

Mott and Gurney’s book to a considerable extent fills this gap. It sets forth modern ideas about ideal and real nonmetallic crystals; a large chapter is devoted to electrical and photoelectric phenomena in alkali-halide crystals; the doctrine of semiconductors and insulators is presented (electrical conductivity and breakdown, the theory of contact between a metal and a semiconductor, and rectifying properties of contacts); special chapters are devoted to luminescence of crystal phosphors and to the theory of photographic processes; some questions in the theory of metal corrosion are considered. As can be seen, the content of the book is very diverse. Nevertheless it constitutes something whole, reflecting the unity of nature of the diverse processes occurring in ionic crystals.

Mott and Gurney’s book is by no means an exhaustive survey. It is, in the main, a theoretical book, in which the experimental material is presented from the standpoint of the theorist, i.e. insofar as it serves as an illustration of the theory, as the basis on which it is built, and as the criterion by which it is tested. The book reflects chiefly the authors’ own works and their own points of view. Theoretical works of other investigators, set forth in passing, play for the most part an auxiliary role.

Mott and Gurney’s book presupposes that the reader is familiar with the fundamentals of solid-state theory and with the basic experimental facts in this field. Thus, for example, band theory is set forth rather concisely; the corresponding paragraphs serve merely as a reminder of what is already assumed to be known to the reader. The book is intended for the physicist who is specially concerned with electronic phenomena in crystals, and not for the student entering this field for the first time. Nevertheless, it is written sufficiently clearly and gives the reader a general idea of the situation in this field.

The first English edition of Mott and Gurney’s book appeared in 1940. The second edition, from which the Russian translation was made, came out in 1948, but in practice it does not differ from the first. It contains only brief additions to certain chapters, in which a concise and far from complete summary is given of work that appeared after 1940. The Russian edition, in turn, differs in no way from the second English one. It contains no additions or notes by the editor. Thus, this book is to some extent out of date. The authors write in the introduction: “We have used the most up-to-date data.” The Soviet reader in 1950 should not trust this statement: theoretic—

theoretical and experimental works of the last decade and, what is especially important, the works of Soviet physicists have practically remained outside the scope of this book. Meanwhile many Soviet works constitute an essential contribution to the development of our ideas about electronic and ionic processes in crystals. Academician A. F. Ioffe, who is the editor of the translation, occupies a leading place in this field of physics. His works and those of his collaborators bear a direct relation to the questions considered in Mott and Gurney’s book. A. F. Ioffe, better than anyone else, could have pointed out the untimeliness of certain propositions in Mott and Gurney’s book. Unfortunately, the hand of the editor is not at all felt in it, unless one counts the brief preface in which the editor confines himself to regrets that the authors do not mention a number of Soviet works.

The book contains a number of minor inaccuracies and defects. The authors define a semiconductor as a solid possessing electronic conductivity which tends to zero as the temperature is lowered. This high-school definition could have been retained at the present time. In fact, there exists a broad group of semiconductors with metallic-type conductivity, which in no way fall under this definition. Incidentally, in Chapter V, when the various types of semiconductors are enumerated, this type of semiconductor is for some reason entirely absent, although it includes many semiconductors (in any case, in the range of low temperatures). On p. 183 a formula is given for the electrical conductivity of a semiconductor, representing the sum of two terms, one of which corresponds to impurity conductivity and the other to intrinsic conductivity. However, impurity and intrinsic conductivities are not additive, and the conductivity of a semiconductor cannot be written in the form of a two-term formula, as the authors do. On p. 184 an incorrect reference to the bibliography is given: Neibur’s work is discussed, while the reference is to de Boer’s work. In the bibliography one and the same article is repeated several times under different numbers (p. 227, Nos. 5 and 12), which testifies to a certain negligence on the part of the publishing editor.

The translation of the book is, generally speaking, well done. In some places the translators follow the English text too literally. Thus, for example, the terms “fast emulsion” and “slow emulsion,” which are literal translations of the English terms, cannot but raise a smile; they are used instead of the Russian terms “low-sensitivity” or “high-sensitivity” emulsions. “Laws of reciprocity” the translators render as “laws of mutuality.” Such strange deviations from generally accepted Russian terminology should not be allowed in translations of scientific books.

The appearance of Mott and Gurney’s book does not remove from the agenda the question of creating a Soviet book on the modern theory of nonmetallic crystals, reflecting the work of Soviet researchers, to whom the leading role in this field of physics undoubtedly belongs.

F. Vol’kenshtein.