The Rutherford Memorial Lecture, 1962 Atomic physics and the strength of metals

Abstract

In the previous Rutherford lecture Sir Lawrence Bragg (1961) gave an account of the history and present position of crystallography. Crystallography consists of the study of the regular ways in which atoms or molecules are arranged in solids, and crystallographers now investigate substances of ever-growing complexity. At the same time, alongside crystallography, there has grown up a science which is related to it, namely, a study of the ways in which these regular arrangements can break down. If there are many thousands of crystal structures known in nature, you would guess that there must be tens of thousands of possible defects; this may be so, but in fact the study of defects is confined at the present time to those which are observed in the simpler crystal structures, in metals, oxides and so on, and so we are far from knowing the full complexity that may exist. Actually, however, there is one form of defect which has a certain simplicity and very great theoretical and practical importance, namely, the dislocation. It is the history and present status of this concept that form the subject matter of this lecture.