Simulation of Phase Transition for Water in Nanoscale Systems by Molecular Dynamics Method

• Main Authors: Hsiu-Wen Chang, 張秀文
• Other Authors: Prof. Chin-Hsiang Cheng
• Format: Others
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/62965528206700568196

碩士 === 大同大學 === 機械工程研究所 === 90 === The present study is concerned with the interface properties during phase transition for water in a control system in nanoscale. Molecular dynamics method (MD) is adopted to predict the kinematic behavior of water molecules in the phase-changing processes, including vaporization, condensation, and solidification. In the molecular dynamics analysis, Newton’s second law of motion governs the motion of any molecules. 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 known. The interactive forces between any two molecules are determined based on Carravetta-Clementi (CC) potential in this study. The van der Waals force and the electrostatic force are evaluated between water molecules and then the translational and angular velocity vectors and the position of the molecules can be predicted. Based on the data of the position and velocity vectors at any instant, the variations in the kinetic and the potential energy have been carried out, and some statistic quantities have been evaluated with ensemble average. The MD study was performed over wide ranges of temperature and density in ensemble average with 256 water molecules in the control volume. The near-critical and the saturated liquid-vapor mixture regions are concerned by in this study. Agreement of the present data is found with previous reports, and the present energy data closely meet the requirement regarding the energy conservation in <NVE> ensemble.