Predicting the Lattice Thermal Conductivity in Nitride Perovskite LaWN3 from ab initio Lattice Dynamics

Using a density functional theory-based thermal transport model, which includes the effects of temperature (T)-dependent potential energy surface, lattice thermal expansion, force constant renormalization, and higher-order quartic phonon scattering processes, it is found that the recently synthesized nitride perovskite LaWN3 displays strong anharmonic lattice dynamics manifested into a low lattice thermal conductivity (kappa(L)) and a non-standard kappa(L)proportional to T-0.491 dependence. At high T, the departure from the standard kappa(L)proportional to T-1 law originates in the dual particle-wave behavior of the heat carrying phonons, which includes vibrations tied to the N atoms. While the room temperature kappa(L)=2.98 W mK(-1) arises mainly from the conventional particle-like propagation of phonons, there is also a significant atypical wave-like phonon tunneling effect, leading to a 20% glass-like heat transport contribution. The phonon broadening effect lowers the particle-like contribution but increases the glass-like one. Upon T increase, the glass-like contribution increases and dominates above T = 850 K. Overall, the low kappa(L) with a weak T-dependence points to a new utility for LaWN3 in energy technology applications, and motivates synthesis and exploration of nitride perovskites.

Automated summary

Using a thermal transport model based on density functional theory, researchers found that the recently synthesized nitride perovskite LaWN3 has strong anharmonic lattice dynamics, resulting in low lattice thermal conductivity and a non-standard temperature-dependent thermal conductivity. At high temperatures, the heat carrying phonons show dual particle-wave behavior, including vibrations tied to the N atoms. While the room temperature heat transport is mainly particle-like, there is also a significant wave-like phonon tunneling effect, contributing to a glass-like heat transport. The low lattice thermal conductivity and weak temperature dependence suggest potential applications in energy technology.