Simulation of phase states for water in nanoscale systems by molecular dynamics method

Molecular dynamics (MD) method is adopted to predict the kinematic behavior of water molecules in various equilibrium states. The range of states considered in the present simulation covers the saturated liquid–vapor mixture region, near-critical region, and supercritical region. Translational and angular velocities as well as the locations of all the molecules can be predicted at any instant when the inertial and external forces acting on the molecules have been determined. The interactive forces between molecules are determined based on Carravetta–Clementi (CC) potential. Based on the data of position and velocity vectors of the molecules at any instant, the variations in potential, kinetic, and total energies of the system during the simulation process toward equilibrium in an 〈NVT〉 or 〈NVE〉 ensemble are investigated, and some statistic quantities have been evaluated by ensemble averaging. The present simulation results for the near-critical region tend to confirm the data provided by Ohara and Aihara [S. Kotake, C.L. Tien (Ed.), Molecular and Microscale Heat Transfer, Begell House, New York, 1994, p. 132; Trans. JSME, Ser. B 60 (1994) 146].