Analysis of the electronic nature and transport properties of Co2CrGe, Co2FeGe, and Co2NiGa by computational electronic structure calculations

Electronic and thermoelectric properties of the full-Heusler materials Co₂CrGe, Co₂FeGe, and Co₂NiGa are studied, using first-principles full potential linearized augmented plane waves method. To treat the exchange correlation, Generalized Gradient Approximation parameterized by PBE-sol with the inclusion of spin polarization is used. The frequency fluctuation order is continual at 300 K after heating to 3 ps with very small distraction in the atomic structure conforming the structure stability of the studied structures. Also inclusion of spin-orbit coupling effect on density of states undermines significant change in peaks specially d-states in the materials and caused a degeneracy. Band structure analysis clarified that states crossing the Fermi level have the importance for enhancing the thermoelectric properties of the materials. The topology of the states indicates a gap at the bulk level, which is the unique character of the heavy elements in the materials Co₂CrGe, Co₂FeGe, and Co₂NiGa. Thermoelectric properties are calculated for a temperature of 300 K using semi-classical Boltzmann's theory implemented in BoltzTraP code. In these calculations, it is found that these materials favor electron doping with having maximum values of ZT in the n-type region.