A computational study of Stillinger–Weber silicon at 0.75 GPa in supercooled region

Abstract

We studied the liquid-liquid transition in supercooled silicon modeled by the Stillinger–Weber potential. The Isothermal Isobaric Monte Carlo (NPT-MC) simulation techniques were performed here to compute the free energy difference between the two liquid phases of silicon by Bennett Acceptance Ratio (BAR) method along with a reversible path at 0.75 GPa pressure and 970 K temperature. The thermodynamic properties as energy ([Formula: see text]) and density ([Formula: see text]) of the high-density liquid (HDL) phase have been computed here at different temperatures from 970–990 K. We also computed the entropy difference between the high-density liquid (HDL) and low-density liquid (LDL) phases which indicates that the glass transition temperature for the LDL phase is lower compared to the HDL phase. Further, by using the BAR method, we have computed the excess Gibbs free energy (G[Formula: see text]) of HDL phase with respect to the crystalline phase at different temperatures in the supercooled region of SW-Silicon potential model. Based on the slope of excess Gibbs free energy with respect to temperature (T), we found that the excess entropy (Se) of the HDL with respect to crystalline phase shows a nonmonotonic dependence on temperature at the liquid-liquid transition temperature of T[Formula: see text] = 970 K. Our results are in good agreement with the previous observation of a nonmonotonic dependence of the enthalpy on temperature in MD simulations, starting with the HDL phase at a temperature just above T[Formula: see text]. All these properties are useful to understand the phase behavior of supercooled silicon and can be applicable to identify the better quality of silicon for industrial uses.