Vibrational properties and lattice thermal conductivity of bulk and monolayer ZrS₂ at finite temperatures

Abstract The traditional three-phonon scattering approach cannot adequately reflect the anharmonic phonon properties of the ZrS 2 system due to its strong intrinsic anharmonicity. In this study, the vibrational properties and lattice thermal conductivity of both bulk and monolayer ZrS 2 were investigated using large-scale machine learning force field molecular dynamics simulations and the anharmonic phonon approach, where all orders of anharmonic interactions between phonons caused by temperature were considered. At finite temperatures, the predicted Raman-active in-plane E g mode of the bulk phase ZrS 2 decreases, while the inter-plane A 1 g mode shifts to the blue, in agreement with experimental observations. Due to the competition between the chemical bond ionicity and phonon anharmonicity, the vibrational stiffness and frequency of the A 1 g mode in monolayer ZrS 2 exhibit inverse temperature-dependent behavior compared to the bulk phase. Phonon linewidths and scattering rates increase significantly with temperature, indicating stronger anharmonic interactions in ZrS 2 . The lattice thermal conductivity of bulk ZrS 2 is significantly reduced when anharmonic phonon scattering beyond three-phonon processes is considered, with an average value of 1.91 ± 0.08 Wm −1 K −1 at 300 K, which aligns with experimental results. Acoustic phonon modes dominate heat transport, with the lifetime of the TA mode being particularly temperature-sensitive. Monolayer ZrS 2 exhibits enhanced lattice thermal conductivity, more than twice that of the bulk, due to the reduced unit cell volume and increased phonon lifetimes.