A new ab initio modeling scheme for the ion self-diffusion coefficient applied to the ε-CuSn phase of the Cu-Sn alloy.

We present a new scheme for modeling of the ion self-diffusion coefficient. Our scheme broadens the applicable scope of the 'ab initio + modeling' approach, which combines modeling of the self-diffusion coefficient with ab initio predictions. Essential concepts in our scheme are 'domain division' and 'coarse-graining' of the diffusion network, according to calculated barrier energies. With the former concept, the diffusion network is divided into a few types of simple disjunct domains. Their networks are further simplified with the latter idea that groups some ion sites and regards them as just a single site. We applied this scheme to Cu diffusion in the ε-Cu3Sn phase of the Cu-Sn alloy and succeeded in reproducing experimental diffusion coefficients in a wide range of temperature.