The vacancy formation and migration enthalpies Hf and Hₘ in tantalum are calculated by means of ab initio pseudopotential techniques. The results obtained after relaxation with supercells containing 54 atomic sites (Hf=3.0 eV and Hₘ=0.8 eV) are in excellent agreement with experiments (Hf=3.1 eV and Hₘ=0.7 eV). The electronic entropy has a moderate influence on their temperature dependence. The effects of structural relaxation, which reduce Hf by 14%, are significantly larger than for group-VI elements and are typical of a normal behavior for the bcc structure. The experimental tracer self-diffusion coefficient is well reproduced within the rate theory using an estimate of the vibrational formation entropy and the attempt frequency.
No takes yet. Share an insight, caveat, or question.
Satta et al. (1999) studied this question.