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.