Ab initio investigation of Co-(V,Nb)-Sn Heusler alloys for thermoelectric applications

Co-(V,Nb)-Sn Heusler alloys are studied within the GGA-PBE and hybrid (HSE06) approaches. From HSE06 calculations, the Half-Heusler structures CoVSn and CoNbSn are semiconductors with bandgaps of 1.33eV and 1.50eV, respectively. On the other hand, the Full-Heusler systems Co2VSn and Co2NbSn have a half-metallic nature and bandgaps of 1.26eV and 0.86eV, respectively. From the analysis of the band structure, high values were found for the effective masses of the structures studied. Furthermore, the results of magnetic moments and chemical bonds are presented, indicating the presence of covalent-polar bonds. Finally, thermoelectric parameters such as Seebeck coefficient (S), electronic conductivity (a), thermal conductivity (kappa), and Figure of Merit (ZT) were determined, including vibrational effects (phonons), thus improving the results that showed good agreement with experimental data. By determining these properties, it is possible to indicate strategies to improve the thermoelectric performance of these materials.