Effect of L21 and XA ordering on structural, martensitic, electronic, magnetic, elastic, thermal and thermoelectric properties of Co2FeGe Heusler alloys

Based on density functional theory (DFT), the structural, martensitic transition, band structure, density of states, elastic, magnetic, and thermoelectric properties of L2(1) and XA ordering of Co2FeGe compound were investigated. The calculated total energy shows that the most stable phase of these compounds is the L2(1) type with ferro-magnetic state using GGA + U approach. In addition, the possible martensitic transition is occurring for L2(1) phase which has minimum energy localized at c/a = 1.02. The electronic density of states (DOS) and band structure of Co2FeGe exhibit a ferromagnetic metallic for both L2(1) and XA phases. From the calculated elastic constants show that the studied phases are elastically anisotropic and satisfies Born's criteria for mechanical stability. Moreover, through the quasi-harmonic Debye model applied in the Gibbs codeand the thermodynamic analyses have also been estimated. Also, the thermoelectric properties for the both L2(1) and XA structures are examined and discussed based on the Seebeck, electrical conductivity and thermal conductivity coefficients.