Comprehensive first-principles studies of structural, dynamical, elastic, electronic, thermoelectric, and thermodynamic properties of Half-Heusler TiGaAu compound

Abstract

The structural, elastic, electronic, dynamical, thermoelectric (TE), and thermodynamic properties of Half-Heusler (HH) TiGaAu compound with valence electron count (VEC) of 8, are investigated usingfirst-principles density functional theory (DFT) in conjunction with Boltz- TraP2 transport modeling. The Type 1 nonmagnetic phase's optimized cubic structure meets the Born mechanical stability requirements and its dynamical stability, which is confirmed by the phonon dispersion's lack of imaginary frequencies. Due to the presence of a heavy Au atom, TiGaAu exhibits pronounced elastic anisotropy and is mechanically strong, stiff, and ductile according to elastic constants. With a moderate band gap, 0.681 eV (mBJ-GGA), the electronic band structure favors balanced electron{hole transport and reveals an indirect semiconductor character. Thermoelectric analysis reveals that TiGaAu has competitive values up to 900K and high Seebeck coeffcients exceeding 1000 μVK-1 at room temperature, with p-type carriers performing marginally better. Effective carrier transport and advantageous band convergence are reflected in the power factor's steady temperature increase. Though mBJ-GGA predicts somewhat higher Seebeck and power factor values at higher temperatures - an improvement ascribed to its more accurate description of electronic structure - the results obtained using GGA and mBJ-GGA are consistent across the whole range. Furthermore, an excellent thermal stability and moderate lattice softening are confirmed by the smooth variation of temperatureand pressure-dependent thermodynamic properties, including heat capacities, entropy, thermal expansion coeffcient, Debye temperature and Grüneisen parameter. TiGaAu is a promising option for high-temperature energy conversion applications as it combines a strong mechanical resilience, stable lattice dynamics and effcient thermoelectric behavior.