Defect Migration in Sollids: Microscopic Calculation of Diffusion Rates

Abstract

Diffusion includes some of the commonest processes on an atomic scale, in which uncorrelated atomic jumps bring about changes in solids. The many predictions of activation energies characterising the temperature dependence of diffusion have high accuracy when good interatomic potentials are known, and a continually improving accuracy from direct quantal calculations. Much more is needed to find the absolute rate at some temperatures. Recent work for both classical and quantum diffusion shows that rates too can be estimated with respectable accuracy. Such calculations highlight basic problems of solid-state defect physics. They alsow offer predictions of techonogical value for diffusion rates in cases where the timescale or physical conditions are too hard for direct experiment. This talk will discuss (a) various ways of obtaining absolute rates, (b) rates of cation diffusion in oxides and their for the so-called Compensation rule (c) issues of charge state in oxides and semiconductors or the motion of shortlived species, and (e) quantum diffusion of hydrogen in metals.