Effect of an Impurity Atom on Clustering of Vacancies

Abstract

The influence of an impurity atom on the formation process of secondary defects has been presented from a kinetic point of view. A random motion of vacancies is described by the theory of stochastic processes and the transition probabilities are constructed in taking account of crystal structures. The unified point of view for the passage time of vacancies and the lifetime of the complex can be obtained by the concept of the mean first passage time in probability theory and this makes it possible to discuss the existence condition of the complex. In actual calculations, the lattice points are grouped into the shells around an impurity atom and the calculations are performed for two cases of aluminum, in each of which the range of the impurity-vacancy interaction extends to the 1st shell, and to the 2nd shell.