First-principles simulation on thermoelectric properties in Bi-Sb System

Abstract

Thermoelectric properties of bismuth-antimony (Bi-Sb) alloy system were simulated on the basis of first-principles calculation, to discuss the potential for thermoelectric devices. Atomistic model structures of Bi-Sb alloy system were devised in the forms of single-crystal bulk and one-dimensional nanowire under the periodic boundary condition. The cell parameters of the bulk model were simulated with respect to temperature by the quasi-harmonic approximation through phonon calculation, and dependences of the Seebeck coefficient on composition, surface condition, and temperature have been demonstrated by using our original methodology in terms of the electronic state of Bi-Sb alloy system. For the single-crystal bulk Bi-Sb models, a meaningful effect of the composition on the Seebeck coefficient has not been observed, whereas a clear difference in phonon dispersion was confirmed between pure Bi and Sb-substituted Bi, leading to the significant difference in thermal conductivity. We clarified that the surface condition is a key point to control the Seebeck coefficient for the nanowire form.