In writing this review, space limitations faced the authors with a choice between presenting an annotated bibliography covering a large area of solid state research on the one hand, or writing a review article in which only a rather small segment of the field would be discussed in a somewhat more detailed and systematic manner. We have decided to adopt the latter proce dure.The selection of topics was based in large measure on a desire to r�view the fields in which substantial progress has been made in recent years so that these pages might serve the purpose of synthesizing a large body of experi mental and theoretical knowledge. In part, the topics presented also reflect the interests of the authors.
POINT IMPERFECTION IN METALS
VACANCIES AND INTERSTITIALSNumerous approaches have been made in the past few years to investigate the nature of vacancies and interstitials in metals. These approaches can generally be classified into two major categories: 1. that which makes use of imperfections present in metals in thermal equilibrium, and 2. that which employs some method of introducing excess imperfections.Volume diffusion.-The typical example of the first approach is the measurement of volume diffusion in pure metals. A review article by Kleppa (1) and an article by Lazarus (2) give sufficient background in the recent development in this field. The activation energy ED of a diffusion process gives the sum of the energy Ef required to form an imperfection and the en ergy Em which is the activation energy for the motion of a diffusing atom into an adjacent imperfection. Some experiments have been proposed to identify the nature of the imperfections (3, 4, 5) i.e., to see whether vacancies or 1 The survey of the literature pertaining to this review was completed in De cember, 1955.