On the imperfections of crystals
Imperfections of crystals may be either of mechanical or chemical nature. As will appear in the course of this investigation, the phenomena related to the chemical imperfections can hardly be understood without a preliminary knowledge of the mechanical defects of the crystals considered. The aim of the following considerations is to give theoretical reasons for the necessity of microscopic cracks even in the most perfect crystals. It will also be shown how the characteristics of these cracks, such as their size, shape, etc., may in principle be determined from the properties which characterize the atoms or ions which constitute the lattice. The author was led to his conclusions presented here in the course of an attempt to reconcile the discrepancy between the theoretical breaking strength of crystals with the observed values for this quantity. It is proposed therefore to consider this special problem first.
© 1929 by the National Academy of Sciences. Communicated February 13, 1929. I am indebted to Dr. A. Goetz of this laboratory for having called my attention to many experimental facts related to the problem under discussion.