Diffusion calculations with two atomic models in h.c.p Zr-Nb diluted alloys

RAMUNNI, VIVIANA PATRICIA; RIVAS, ALEJANDRO MARIANO FIDEL

MATERIALS CHEMISTRY AND PHYSICS

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2017 vol. 197 p. 163 - 180

0254-0584

In this work we perform a comparison of atomic diffusion multi-frequency models for  h.c.p. lattices. Specifically, in diluted h.c.p. Zr-Nb alloy, we calculate, the tracer self- and impurity diffusion coefficients, with Ghate´s eight frequencies model [1] and with the 13 frequencies model recently developed  by Allnatt et al. [2]. For the latter we investigate the tight-binding limit and the 5-frequency limit of the model. Our exhaustive calculations have been performed using, for both models, classical molecular static techniques (MS), as well as, quantum ab-initio calculations within both LDA and GGA approximations. Our ab-initio calculations show that a, so called, 5-frequency model, without pairs dissociation nor anisotropy in the jump frequencies, that only needs three frequencies, is  sufficient to obtain solvent and solute anisotropic diffusion coefficients that are in agreement with experimental data.[1] P. Ghate, Phys. Rev. 133, A1167 (1964).[2] A. R. Allnatt, I. V. Belova and G. E. Murch, Phil. Mag. 94:22, 2487-2504 (2014).