汽液界面表面张力模拟中的影响因素

The Effect Factor of Surface Tension of Liquid/Vapor in Molecular Dynamics Simulation

用分子动力学模拟方法研究汽液界面性质时 ,适当选取模拟分子数目和势函数截断半径 ,既能满足合理的计算时间要求 ,又减少分子数目效应和势函数截断半径对计算结果的影响。在NVT系综中 ,以氩原子为对象 ,对长方形模拟盒中粒子数目为 5 0 0、86 4、1372和 2 0 4 8个的汽液平衡系统进行模拟计算。在计算时发现 ,汽液界面的表面张力值与模拟分子数目有关 ,模拟分子数目在 10 0 0个以上 ,表面张力值趋于恒定。势函数截断半径Rc=4 .5σ ,计算结果与实验值吻合较好。

It is important to select suitable molecular numbers and cut-off radius of interaction potential to study the surface tension between liquid phase and vapor phase by molecular dynamics simulation, which could both save the computer CPU time and reduce the effect of molecular numbers and cut-off radius of interaction potential on calculating results of simulation. The systems of vapor and liquid phase equilibrium, of which molecular numbers are 500,864,1 372 and 2 048,are simulated by selecting Argon as working substance and using Lennard-Jones potential in the rectangle simulation box. It is shown that the simulation result of surface tension is related to simulation molecular numbers. When the molecular numbers exceed 1 000 molecular the simulation result of surface tension tends to constant value. Under the condition of the cut-off radius of potential being equal to 4.5σ, the simulation result of surface tension agrees with experimental value.