A modified thermodynamic model (Tm-model) for the impurity diffusion in group V and VI metals was developed, which took account of nearest-(NN) and next-nearest (NNN) neighbor monovacancy jumps. The correlation factor f was separately calculated with the aid of Monte Carlo simulation. The calculation of f was based on a nineteen-frequency model for mixed NN and NNN jumps. The comparison of calculated and experimental diffusion coefficients reveals good agreement for several systems. On the other hand, it became obvious that the Tm-model was not applicable to the diffusion of group VIII metals in metals of groups V and VI.

A Modified Thermodynamic Model for the Impurity Diffusion via Nearest- and Next-Nearest Neighbour Jumps in Body-Centred Cubic Metals of the Groups V and VI. G.Neumann, V.Tölle, C.Tuijn, H.Bakker: Physica B, 1997, 233[2-3], 161-72