A Simulation Study of Equilibrium States in Supercooled Stillinger—Weber Silicon

In the supercooled liquids which are prone to crystallization, identification of properties of  metastable equilibrium liquids can be challenging.  In case of supercooled silicon, modeled by the Stillinger—Weber (SW) potential  [F. H. Stillinger and T. A. Weber, Phys. Rev. B. 32, 5262 (1985)], several earlier studies have identified 1060 K as the lowest temperature at which it is possible to equilibrate the liquid at zero pressure.  We discuss how the equilibrium liquids at or above 1060 K can be identified based on free energy calculations [P. A. Apte and A. K. Gautam, J. Stat. Phys.  149, 551 (2012)].  In particular the Gibbs free energies of these liquids must satisfy the Gibbs--Helmholtz relation for equilibrium states.  Further we also find that the potential energy distributions generated through isothermal isobaric simulation trajectories at various temperatures follow the equilibrium temperature—potential energy curve closely.   We also discuss some interesting aspects of relaxation of the supercooled liquids  vis-a-vis the properties of the equilibrium states.