(51b) Nonmonotonic Dependence of the Absolute Entropy On Temperature in Supercooled Stillinger-Weber Silicon



Using a recently developed thermodynamic integration method, we compute the precise values of the excess Gibbs free energy (Ge) of the high density liquid (HDL) phase with respect to the crystalline phase at different temperatures (T) in the supercooled region of the Stillinger-Weber (SW) silicon [F. H. Stillinger and T. A. Weber, Phys. Rev. B. 32, 5262 (1985)]. Based on the slope of Ge with respect to T, we find that the absolute entropy of the high density liquid (HDL) phase shows a nonmonotonic dependence on temperature at 1065 K close to the liquid--liquid transition temperature of TLL=1060 K. Our result is consistent with the earlier observation of a nonmonotonic dependence of the enthalpy on temperature in molecular dynamics simulations starting in the HDL phase at a temperature just above TLL [S. Sastry and C. A. Angell, Nat. Mater. 2, 739 (2003)]. Our result elucidates a thermodynamic route by means of which the liquid--amorphous transition occurs in SW silicon, and possibly, in real silicon.
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