First-Principles Predictions of the Structural, Elastic, Electronic, Magnetic, and Thermal Properties of Equiatomic FeMnLiSi and FeMnLiGe Quaternary Heusler Alloys

In this work, first-principles calculations based on density functional theory were employed to investigate the structural, elastic, half-metallic, magnetic, and thermal properties of two novel quaternary Heusler alloys, FeMnLiSi and FeMnLiGe. The results revealed that ferrimagnetic FeMnLiSi and FeMnLiGe with type III structures were energetically the most stable, and possessed thermodynamic, dynamic, and mechanical stabilities. Their equilibrium lattice constants were 5.6104 Å and 5.7479 Å. At equilibrium, FeMnLiSi and FeMnLiGe exhibited brittleness, elastic anisotropy, and half-metallic ferrimagnetism, with half-metallic band gaps of 0.7935 eV and 1.0805 eV, respectively. The total magnetic moments per unit cell of FeMnLiSi and FeMnLiGe were both 2.0000 µB, which conforms to the Slater-Pauling rule. Their half-metallic ferrimagnetism remained robust over a broad range of uniform lattice strains. FeMnLiSi exhibited a higher stability, melting point, and Debye temperature, as well as a narrower half-metallic gap, than FeMnLiGe. This work systematically predicted the intrinsic structural, mechanical, magnetic, and thermal properties of FeMnLiSi and FeMnLiGe, and delivered theoretical insights for designing new Heusler-type half-metallic candidates.