Phase stability and physical properties of XSnPt(X = Ti, Zr, Hf): A density functional theory study

Based on the density functional theory (DFT) with the GGA functional, we investigated the structural, electronic, mechanical, phonon, and thermal properties of TiSnPt, ZrSnPt, and HfSnPt half-Heusler alloys using VASP and CASTEP codes. The negative heat of formation and cohesive energy values confirm the thermodynamic stability of all three alloys, suggesting their plausible experimental synthesis. Band structure calculations using GGA, GGA+SOC, and HSE06 show semiconducting behavior with indirect band gaps; SOC reduces the band gap, while HSE06 increases it. Mechanical and phonon dispersion results confirm the alloys’ mechanical and dynamical stability. The bulk-to-shear ratios and high melting points ($>$1000 K) indicate good ductility. Room-temperature lattice thermal conductivities k${}_l$ are 15.3, 16.7, and 16.4 W/m K for TiSnPt, ZrSnPt, and HfSnPt, respectively, with nearly isotropic phonon transport. The k${}_l$ decreases with temperature due to enhanced Umklapp scattering, reaching $\approx$4.5–5.0 W/m K at 1000 K. These results highlight the alloys’ potential for high-temperature structural and thermoelectric applications.