Structural, Electronic, Half-Metallic and Thermoelectric Properties of Quaternary Heusler Alloys AgCoFeZ (Z = Al, Ga, Si, Ge, and Sn), NiFeCrZ(Z = Al, Si, Ge, In) and NdCoMnGa: a First Principles Study

The full-potential linearized augmented plane wave (FP-LAPW) approach of density functional theory has been utilized to systematically analyze the AgCoFeZ(Z = Al,Ga,Si,Ge, Sn), NiFeCrZ(Z = Al,Si,Ge,In) and NdCoMnGa materials. The electronic band structure and density of states (DOS) are determined using GGA, GGA + U, mBJ, mBJ + U and SCAN approximations. AgCoFeGe, AgCoFeSn, NdCoMnGa and NiFeCrAl exhibit half-metallic (HM) properties when their equilibrium lattice constants are optimally adjusted in the normal state and themagnetic moment of the alloys satisfies the value prescribed by the Slater-Pauling rule.We have analyzed the calculated DOS and energy bands of the alloys, and investigated the mechanism behind the formation of the HM band gap based on our research findings. The excellent HM property gives a good candidate for spin polarized material. Using spin density functional theory calculations, it is found that the given compounds are metallic in both spin channels. The thermoelectric properties have also been investigated in terms of Seebeck, electrical conductivity, thermal conductivity, power factor and figure of merit.