First principles electronic structure, magnetic, thermoelectric and optical properties of ferrimagnetic half-heusler compound TaMnX (X = Si,Ge): A DFT+U study

Abstract Density Functional Theory calculation using Hubbard U parameters was performed to study the electronic, magnetic and physical properties of TaMnX (X = Si, Ge) compounds. For the exchange-correlation functional, the projector augmented wave method with the Generalized Gradient Approximation was used. The compounds exhibit negative formation energies—lower than those of competing phases along with mechanical and dynamical stability, indicating they are experimentally synthesizable. The spin-resolved band structure reveals that TaMnSi and TaMnGe are half-metallic, with respective indirect down-spin band gaps of 0.7 eV and 0.6 eV. Each compound possesses a magnetic moment of −2 μ B , consistent with the Slater-Pauling rule. These alloys are ductile and anisotropic in nature. Thermoelectric properties calculated using BoltzTraP2 reveal low lattice thermal conductivity and high Seebeck coefficient, power factor and figure of merit with increasing temperature. Furthermore, optical property calculations indicate high optical conductivity in the ultraviolet and visible regions. The compounds also exhibit high reflectivity and extinction coefficient at low photon energies. These characteristics suggest that TaMnX compounds are not only viable candidates for spintronic applications but also energy-efficient materials with promising potential in optoelectronic devices such as photodetectors, ultraviolet sensors, and solar cells.