Crystal growth kinetics in BaS semiconductor: Molecular dynamics simulation and theoretical calculations

Understanding the liquid-solid phase transition mechanisms and dynamics is of boundless scientific significance, and holds enormous technological relevance in designing mono or polycrystalline materials with tailored microstructures and property combinations. However, the atomistic mechanisms controlling these processes, and their associated theoretical models, remain elusive for most materials. In this article, we employ molecular dynamics (MD) simulations to investigate the crystal growth kinetics of a barium sulfide (BaS) semiconductor, used here as a model substance for which a reliable interatomic potential is available. The crystal growth velocities, v(T), were estimated within two temperature intervals: at shallow supercooling, where spontaneous nucleation could not be observed within the MD time scale, v(T) data were obtained by the embedded-seed method, and at deep supercooling, where spontaneous nucleation was detectable, v(T) were computed directly from brute-force atomistic simulations. Relevant properties of the material, including density, enthalpy, and the self-diffusion coefficients, were also determined as a function of temperature. The growth rate data were analyzed using three classical theoretical models. The results indicate that the diffusion-controlled model using the screw dislocation mechanism and the kinetic phase-field model accurately describe the MD-derived v(T) at both shallow and deep supercooling levels. However, only the diffusion-controlled theory using screw dislocation growth successfully captures the v(T) peak, as predicted by all crystal growth theories and observed in the simulations.