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

Abstract

The binding energies are calculated between a vacancy and an interstitial impurity (like carbon) atom in b.c.c. transition metals (a-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.Die Bindungsenergie zwischen einer Leerstelle und einer Zwischengitterstorstelle (wie Kohlenstoff) in k. r. z. ubergangsmetallen (a-Fe, Mo und W) wird berechnet. Die dnderungen der Gesamtenergie infolge der Einfiihrung von Gitterdefekten werden mit einer ,,tight-binding"-Elektronentheorie

A Review of some Theoretical Models for Point Defect Calculations

“…Friedel rule was introduced for selfconsistency up to the nearest neighbour of the vacancy. Masuda [38] applied this model in case of BCC metals.…”