Anomalous pressure dependence of lattice dynamics in PbTe: a simulation study

Understanding the high-pressure lattice dynamics is crucial to modulate the thermal transport in thermoelectric materials beyond ambient environment. Herein, using molecular dynamics simulations in combination with an accurate machine-learning potential, we find an anomalous non-monotonic pressure dependence of the frequency of the transverse acoustic (TA) phonon in PbTe. The longitudinal acoustic (LA), longitudinal optical (LO) and transverse optical (TO) phonons harden as expected when pressure increases. The well-known double-peak feature of the TO mode in PbTe gradually vanishes when pressure is enhanced. The theoretical results are compared with available experimental data to verify our calculations. Moreover, we have also calculated the lattice thermal conductivity under pressure and revealed the phonon transport mechanism.