Transport of Ce-Co-Sb skutterudites

The correlation among composition, structure, chemical bond and transport of unfilled skutterudite CoSb₃ and filled skutterudite CeCo₅Fe₃Sb₁₂ has been studied using the density function and discrete variation (DFT-DVM) method. Three models for filled skutterudite study were proposed and calculated to describe the "rattling" pattern. Model 1 is with Ce in the center, model 2 is with Ce away from the center and near to Sb, and model 3 is also with Ce away from the center but near to Fe. Due to the different changes between ionic and covalent bonds, there is less difference in stability among the models 1, 2 and 3. Therefore, these different models can exist at the same time, or can translate from one to another more easily. In other words, the "rattling" pattern has taken place. The covalent bond of Co-Sb or Fe-Sb in filled models is weaker than that of Co-Sb in unfilled models, as an electrical cloud of Sb takes part in the covalent bond of Ce-Sb in the filled models. The result is consistent with the experimental result that the thermal conductivity of CeCo₅Fe₃Sb₁₂ is lower than that of CoSb₃, and the thermoelectric property of CeCo ₅Fe₃Sb₁₂ is better than that of CoSb ₃