Bi₂Te₃の電子構造とゼーベック係数

抄録

Bismuth tellurides have been studied for investigating their electronic structures by using the discrete variational X α method. The systems not only Bi₂Te₃ but also the Se or Sb substituted-Bi₂Te₃ were calculated with setting threekinds of cluster corresponding to the base structure of Bi₂Te₃; cluster C-1: Bi₇Te₆, cluster C-2: Bi₆Te₇ and cluster C-3: Bi₃Te₁₀. The conditions for the calculation are non-relative and relative theories, non-spin and the crystal group of C3V. The cleavage and bond strength of the Bi₂Te₃ structurewere cleared through the calculations. The Se substituted-Bi₂Te₃ led to the ionic structure of Bi₂Te₃ of the base material and to the n-type thermoelectricity. Furthermore, the substitution with Sb atom caused the positive charge with rather covalent bonding nature than that in Bi₂Te₃, leading to the p-type. The relativistic calculation significantly indicated the weaker bond of Te-Te which places related to the cleavage and the contribution of 5d electrons of Bi appeared in the higher energy level.