Puzzling solid-liquid phase transition of water(mW) from free energy analysis: A molecular dynamics study

Abstract

Water shows a very different trend while melting. Estimating the transition point of any material is still problematic. In recent time, several techniques have been involved to simplify things. Due to anomalous behaviors of water, it’s transition properties are different from conventional substances. This study is an approach to understand the mechanism of phase transition using computer simulation. For better understanding the mechanism, it is vital to have knowledge of interatomic interaction of the water system. There are several potential models available for water like SPC/E, TIP3P, TIP4P etc. Another potential model, Stillinger-Weber potential model is good enough to predict the properties of water. This model considers two and three particle interactions. That model of water is named as monoatomic water(mW). The Anomaly behaviors of water are well predicted using mW model of water. Difference in free energy connecting two phases of water is evaluated using reversible thermodynamic route. Supercritical path is established using more than one path. These thermodynamic paths are reversible. The best of my knowledge, this is first approach to apply thermodynamic path for a system where volume of solid state is more compare to volume of liquid during phase transformation. Transition point is determined Gibbs free energy. Abrupt change in the density as function of temperature is observed. Hysteresis loop is also observed for potential energy. For temperature higher than 285K, huge fall in density and potential are noticed, suggesting full transition from one phase to another