Theoretical calculations of the properties of point defects in solids

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Abstract
In accordance with the terms of reference of this series of journals, we have set out in this review to give as far as is possible a critical overview of the methods currently available for the calculation of the various properties of point defects in, first, ionic crystals and, then, in metals. We have restricted ourselves to these two classes of solids since, at present, such calculations as have been made for other materials are relatively few in number and, in our opinion, relatively unreliable. In attempting to write a critical review of this area we have found it impossible to restrict our discussion entirely to relatively recent papers. For example, when we are discussing ionic crystals, it is essential that we review the Mott-Littleton method, and the original paper by these authors appeared in 1938. The real upsurge in interest in the type of calculation we are reviewing largely parallels the development of modern electronic computers. Thus, such calculations as have been made recently can be regarded as computer “experiments.” In a recent short review, Gilman' has justifiably pointed out that there comes a point at whch, from a “cost effectiveness” point of view, it becomes more economical to spend money doing real experiments on real crystals instead of computer experiments on model crystals. This is a valid point and should be borne in mind when assessing the relative merits of the types of defect calculations we discuss. In fact, there is a real danger in writing a “critical” review of this field in that one may convince the reader that the whole subject is an intellectual dead end, and we have tried to bear this in mind in our subsequent discussion.