Chemical diffusion by vacancy pairs in intermetallic compounds with the B2structure

This paper is concerned with the implications of vacancy-pair mechanisms on chemical diffusion intermetallic compounds with the B2 structure, The disc ussion specifically includes the so-called triple-defect mechanism. It is s hown that the vacancy-pair mechanism cannot contribute to chemical diffusio n in the intermetallic compound at the stoichiometric composition. AB. Focu sing on the triple-defect mechanism we extend it to non-stoichiometric comp ositions by including isolated antistructural atoms. By means of Monte Carl o simulation we show that the efficiency of the triple-defect mechanism in providing for chemical diffusion increases linearly with increasing antistr uctural atom composition but the efficiency remains relatively low unless t he composition is highly non-stoichiometric.