Theoretical modeling of Te doped CoSb3

The electronic structure of the Te doped CoSb₃ skutterudite is investigated by means of fully periodic density functional theory (DFT) calculations. Since the geometrical structure of a material may strongly affect its properties, Te substituted for Sb (Co₄Sb₁₁Te) and Te fully filled (TeCo₄Sb₁₂) cobalt skutterudite are both studied in order to understand where Te atom is sitting. From the analysis of the geometry and electronic structure properties, the Te filled system is ruled out. The extent of the change transfer among Co, Sb and Te atoms is evaluated using the Quantum Theory of Atom in Molecules (QTAIM). Te substitution for Sb yields a conductor with Fermi energy lying in the conduction bands zone of unsubstituted CoSb₃. The Seebeck coefficient S and the electrical conductivity σ are calculated using the semiclassical Boltzmann monoelectronic transport theory. Computed S values agree with experimental evaluations on nanostructured Te doped CoSb₃ samples when the frozen band approximation is used for low Te doping and the Co₄Sb₁₁Te band structure is adopted for high Te content.