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Project Summary: Accurately characterizing the phonon dispersion and lattice thermal conductivity of large-scale two-dimensional (2D) transition metal dichalcogenide (TMD) systems is challenging for first-principles methods due to the computational cost. Empirical molecular dynamics can be used for this purpose, as thermal transport in 2D TMDs is dominated by phonons. This approach requires an accurate force field.
In this work, we developed a new reactive force field, ReaxFF2024, using a relatively small set of density functional theory (DFT) calculations. ReaxFF2024 significantly improves the accuracy of phonon dispersion relations in 2D molybdenum disulfide (MoS2) while retaining the ability to describe reactive dynamics. Compared to the prior ReaxFF2017, ReaxFF2024 reduces the zone-center optical phonon frequencies of A2′′ and E′ modes from 1438 cm−1 and 822 cm−1 to 456 cm−1 and 358 cm−1, aligning closely with the DFT values of 461 cm−1 and 367 cm−1. The predicted phonon thermal conductivity (κ∞) of 73 WK−1m−1 is within the range of experimental measurements. This marks the first time that ReaxFF force field has been explicitly optimized to describe lattice dynamics. Our methodology can be readily extended to other emerging TMDs, their alloys and heterostructures, including defective systems.
Publication: Wang, T., Marmolejo-Tejada, J.M., Mosquera, M. A., Crespi, V.H., and van Duin, A.C.T.(2025) New ReaxFF Reactive Force Field Optimized forVibrational and Thermal Properties ofMolybdenum Disulfide. J. Phys. Chem. Lett. 16, 4529−4535.
DOI: 10.1021/acs.jpclett.5c00464
2DCC Role:The 2DCC theory facility was used for ReaxFF force field development to predict vibrational and thermal properties of 2D MoS2 system. This project included 2DCC, Penn State Mechanical Engineering and users from Montana State University.