A model was proposed for the simulation of the diffusion of impurities in body-centred cubic atomic lattices. It involved the three-dimensional volume being divided into small cubical elements (voxels), containing more than one atomic cell each. Once the domain was discretized, impurities jumped from one voxel to another according to a probability that took into account the composition and geometry of the target voxel. In the present work, the model was applied to a prismatic volume and, in order to deduce the relationship between the atomic jumping frequency and the temperature, two different cases were studied. One consisted of a Fe matrix with Cr impurities, and the other was based upon a Cr matrix with Fe impurities. The results obtained from these simulations were compared with profiles obtained by Dictra software. The results for the atomic jump frequencies were fitted to an Arrhenius-type equation; giving,

JCr(/s)= 3.396 x 1018exp[-306421/RT]

and

JFe(/s)= 1.096 x 1019exp[-411729/RT]

From these equations it was possible to obtain an activation energy for the atomic jumping phenomenon of about 306kJ/mol, and about 411kJ/mol for the Fe-matrix and Cr-matrix systems, respectively. These energies matched the empirical measured values for the diffusion of Cr and Fe impurities, 250 and 407kJ/mol, respectively. The results obtained here ensured that the proposed model was suitable for simulating the three-dimensional diffusion of substitutional impurities in Cr and Fe body-centred cubic systems. It could be easily expanded to other body-centred cubic matrix systems.

Diffusion Simulation of Cr-Fe BCC Systems at Atomic Level Using a Random Walk Algorithm. I.San Sebastian, J.Aldazabal, C.Capdevila, C.Garcia-Mateo: Physica Status Solidi A, 2008, 205[6], 1337-42