Extensive DFT study of FeMnCrGe quaternary Heusler alloy: structural, elastic, magnetic, optical and thermoelectric properties

Abstract

This study employs first-principles density functional theory (DFT) to comprehensively investigate the structural, electronic, magnetic, optical, and thermoelectric properties of the FeMnCrGe quaternary Heusler alloy, an unexplored material. Using the WIEN2k simulation package, the crystal structure was optimized with the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method and the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA). The optimized lattice constant of 5.8076 Å and a negative formation energy confirm the alloy’s thermodynamic stability. Elastic analysis reveals a brittle nature, with a high Young’s modulus and a Poisson ratio of 0.229, indicating the predominance of covalent bonding. The computed electronic structure verifies the alloy's half-metallic nature, with the spin-up state acting as a metal and the spin-down state as a semiconductor. This behavior is accompanied by an indirect band gap (Γ-X) of 0.974 eV, determined via the mBJ approximation. The total magnetic moment of 1.00 μB demonstrates the compound's compliance with the Slater-Pauling rule, affirming its stable ferromagnetic nature. Characterized by a high refractive index across the visible wavelengths, as well as strong ultraviolet absorption, this material is highly suitable for photovoltaic use. The alloy’s thermoelectric performance, assessed with the BoltzTraP code, is marked by a Seebeck coefficient of 124.1 μV K⁻¹ and a figure of merit of 0.42 at 500 K, suggesting its effectiveness for energy conversion. These insights highlight FeMnCrGe's potential as a multifunctional material for spintronics and photovoltaics and suggest experimental validation for practical implementation.