Comprehensive analysis: Exploring quaternary Heusler alloys CoFeXGe (X = Hf and Ta) through first-principles calculations

The research focused on the quaternary Heusler alloys CoFeXGe (with X being Hf or Ta) using a first principles approach via density functional theory and the Wien2k code. The alloys demonstrated a stable ferromagnetic ground state and exhibited negative formation energies, suggesting their experimental synthesis feasibility. Investigation of the electronic properties revealed that both materials are half-metallic ferromagnets. The calculated indirect band gaps of CoFeHfGe and CoFeTaGe are 1.46 and 0.77 eV, respectively. The mechanical stability of the materials was confirmed through elastic constants analysis. To gain insights into the materials optical behavior and their potential applications in photonics and related fields, correlation of interband optical transitions with electronic band structure was carried out. Finally, Boltzmann transport theory was utilized to evaluate the thermoelectric potential of these alloys over a temperature range extending from 100 to 1000 K.