Design of Heusler alloys using Co-VB-Sn (VB = V, Nb, Ta) atoms within ab initio calculations for thermoelectric applications

Abstract

Environmentally friendly energetic matrices are essential for sustainable human development. In this perspective, Heusler alloys have shown to be promising materials for thermoelectric applications. This work presents a theoretical study of Co-VB-Sn (VB = V, Nb, Ta) Heusler alloys within the GGA-PBE and hybrid (HSE06) approaches. The cubic (C1b) CoVSn, CoNbSn and CoTaSn Half-Heusler compounds exhibit semiconductor characteristics and a bandgap of 1.33eV, 1.50eV and 1.18 eV, respectively, when Co occupies the Wyckoff 4c site. The cubic (L21) Co2VSn, Co2NbSn and Co2TaSn Full-Heusler are half-metallic compounds with a bandgap of 1.26eV, 0.86eV and1.36 eV. All the systems present a total magnetic moment in agreement with the Slater-Pauling rule. The chemical bonds analyses indicate covalent-polar bonds in the studied alloys. High effective mass was found to semiconductors structures, an excellent result in relation to application as thermoelectric. Using Wannier functions, and based in experimental data present in the literature it was studied the thermoelectric parameters for the CoTaSn alloy. Keywords: Heusler alloys. Co-VB-Sn. Thermoelectric materials. DFT. Effective mass.