New ReaxFF Reactive Force Field Optimized for Vibrational and Thermal Properties of Molybdenum Disulfide

Accurately characterizing the phonon dispersion and lattice thermal conductivity of realistic large-scale two-dimensional (2D) transition metal dichalcogenide (TMD) systems usually requires extensive simulations that are challenging at a first-principles level. We present ReaxFF2024, a new reactive force field developed using a relatively small set of density functional theory (DFT) calculations that significantly improves the accuracy of phonon dispersion relations in 2D molybdenum disulfide (MoS2) while retaining the ability to describe reactive dynamics. ReaxFF2024 reduces the frequencies of the zone-center A2″ and E′ optical modes from 1438 cm–1 and 822 cm–1 in the prior ReaxFF2017 force field to 456 cm–1 and 358 cm–1, aligning closely with the DFT values of 461 cm–1 and 367 cm–1. ReaxFF2024 predicts a phonon thermal conductivity (κ∞) of 73 W K–1 m–1, within the range of experimental measurements. This methodology can be straightforwardly transferred to other emerging TMDs and their heterostructures, including defective systems.