Self-diffusion in Zn4Sb3 from first-principles molecular dynamics

The Zn4Sb3 system is promising for thermoelectric applications due to its very low thermal conductivity coupled with a good power factor. Molecular dynamics calculations based on density functional theory were carried out for different stoichiometries of Zn4Sb3, corresponding to three situations: the composition Zn3.6Sb3 (actually Zn6Sb5 with only one Zn site occupied), a slightly higher Zn content Zn3.8Sb3 (with some of the Zn atoms in interstitial sites), and a slightly lower Zn content Zn3.4Sb3 (with some Zn vacancies). The diffusivity was calculated for different temperatures and the diffusion coefficient plotted in Arrhenius plots. The results compare well with experimental data, and point to a highly mobile Zn species with a very high diffusion coefficient prefactor.