On the interaction between a vacancy and an interstitial impurity atom in B.C.C. transition metals

Abstract

AbstractThe binding energies are calculated between a vacancy and an interstitial impurity (like carbon) atom in b.c.c. transition metals (α‐Fe, Mo, and W). The changes in the total energy due to the introduction of lattice defects are calculated using a tight‐binding type electronic theory and the Born‐Mayer repulsive potential. A comparison is made with previous theoretical calculations as well as with recent experimental observations (positron annihilation experiments). In addition the detailed electronic structure is investigated of the impurity atom, assuming both, interstitial and substitutional occupations and using the recursion method by Haydock et al. It is shown that there are marked differences in the local p‐orbital density of states between the octahedral and substitutional impurity (carbon) atoms. These calculations enable one to understand the stability of the vacancy‐interstitial impurity pair in b.c.c. transition metals.