Chemical diffusion by vacancy pairs in intermetallic compounds with the B2 structure

Abstract

This paper is concerned with the implications of vacancy-pair mechanisms on chemical diffusion in intermetallic compounds with the B2 structure. The discussion specifically includes the so-called triple-defect mechanism. It is shown that the vacancy-pair mechanism cannot contribute to chemical diffusion in the intermetallic compound at the stoichiometric composition AB. Focusing on the triple-defect mechanism we extend it to non-stoichiometric compositions by including isolated antistructural atoms. By means of Monte Carlo simulation we show that the efficiency of the triple-defect mechanism in providing for chemical diffusion increases linearly with increasing antistructural atom composition but the efficiency remains relatively low unless the composition is highly non-stoichiometric.