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.