First-principles study of electronic, magnetic, optical, elastic, and thermoelectric properties of quaternary heusler alloys Co2MnSixGe1-x under dilution effect

This study thoroughly investigates the structural, elastic, magnetoelectronic, thermoelectric, and optical properties of Co₂MnSi_xGe_1-x Heusler alloys as a function of Si concentration. The full-potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT) is employed, using the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) parameterization to study compositional effects. Additionally, the GGA-mBJ approximation is used to improve the prediction of the energy gap. The results reveal consistent mechanical stability and ferromagnetic behavior across the compositions. The alloys retain their half-metallicity in accordance with the Slater-Pauling rule. Structural transitions from cubic to tetragonal phases are observed depending on the Si content. Thermoelectric performance and optical responses are highly sensitive to composition, highlighting the strong potential of these materials for applications in spintronics, thermoelectric devices, and optoelectronics.