Large-scale reactive molecular dynamics simulations of structural transitions in transition metal dichalcogenides

We present extensive molecular dynamics (MD) simulations of structural phase transitions in transition metal dichalcogenides (TMD). These quasi-two-dimensional materials are described by the general formula MX₂ with M a transition metal atom (Mo, W, etc) and X a chalcogen atom (S, Se, Te). The crystal structure of a TMD consists of Van der Waals bonded layers, resembling that of graphene. TMDs are hosts of exotic quantum states with potential technological applications. Our work is motivated by recent experiments on MoTe₂, showing diffuse scattering in the vicinity of the 1T'-Td structural transition which is indicative of stacking disorders resulting from layer misalignments along the c-axis. We performed large-scale MD simulations based on reactive force field potentials to investigate the kinetics of this intriguing first-order transition. In particular, our results show that the transition can be viewed as a sequence of 2D structural transitions as the system goes through a series of local free-energy minima.