Understanding the role of non-analytical corrections in phonon transport and thermal conductivity in half-Heusler alloys

Abstract

Dipole–dipole interactions, while normally associated with polar materials, can indirectly affect lattice thermal conductivity by altering phonon dynamics and increasing anharmonicity. In this study, we look at the effect of long-range dipole–dipole interactions in NbYPb (Y = Co, Rh, Ir) half-Heusler alloys using non-analytical corrections (NACs) in phonon calculations. The structural stability of the alloys is calculated using the Birch–Murnaghan equation of state, while phonon dispersion validates their dynamic stability. We calculate phonon lifetimes and lattice thermal conductivity using density functional perturbation theory and the Boltzmann transport equation, both with and without NAC. Our findings show that NAC affects phonon spectra through LO–TO splitting at the Γ-point, influencing lattice thermal conductivity. NAC specifically increases thermal conductivity by 1.86% in NbCoPb and 2.2% in NbIrPb but decreases it by 3.8% in NbRhPb due to variations in LO–TO mode coupling. Thermoelectric transport properties show that p-type NbCoPb has the highest power factor of 39 × 10−4 W/m K2 at 1000 K among the three alloys. Furthermore, size-dependent thermal conductivity estimates indicate that nanostructuring can significantly reduce lattice heat transport, hence increasing the thermoelectric figure of merit. These results provide new avenues for thermoelectric performance optimization and emphasize the significance of dipole–dipole interactions in controlling phonon transport in weakly polar half-Heusler compounds.