Evaluation of Thermal Transport Properties for Verification of Inter-atomic Potentials for WS₂ and WSe₂ Crystals

Transition metal dichalcogenides (TMDs) have been emerging as a new class of two-dimensional layered materials due to their astonishing properties. For applications such as thermoelectric devices or overcoming general overheating issues, understanding and characterization of thermal transport is very important for efficient engineering of 2D TMD materials. Using particle swarm optimization (PSO), we obtain Stillinger-Weber type empirical potential parameters for single-layer WS₂ and WSe₂ crystals. Our results are quite consistent with first-principles calculations in terms of bond distances, lattice parameters, elastic constants and vibrational properties. The effect of temperature on phonon energies and phonon linewidth are investigated using spectral energy density analysis. Calculated frequency shift with respect to temperature is compared to experimental data, demonstrating the accuracy of the generated inter-atomic potentials. Also, the lattice thermal conductivities of these materials are evaluated by means of classical molecular dynamics simulations. The predicted thermal properties are in very good agreement with the ones calculated from first-principles.