Local structure of interstitial Zn in β-Zn4Sb3

The low thermal conductivity of the thermoelectric material beta-Zn4Sb3 has been linked to disorder arising from multiple interstitial Zn sites. Here we investigate the energetics and local distortions associated with these interstitial sites via DFT calculations. Our results show the beta-Zn4Sb3 structure is able to distort into many inequivalent geometries of similar energies, suggesting a topology rich with transport pathways through energetically accessible metastable states. The occurrence of such a shallow energy landscape may explain the recently discovered liquid-like diffusivity of Zn in beta-Zn4Sb3 - comparable to that found in superionic conductors. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.