模拟盒参数对汽液体系模拟过程的影响

为探讨模拟盒参数对分子动力学模拟影响这个长期被忽略的问题,采用Verlet-List搜寻法和Leapfrog差分算法,对分子数目为1000的汽液共存体系进行分子动力学模拟,得到了系统温度为100K时,汽液两相密度、表面张力随系统切片数、汽相空间尺寸、液膜厚度以及步长等模拟盒参数的变化情况.研究结果表明,系统切片数不会影响表面张力及两相密度;体系z轴无量纲长度为60时,模拟值与实验值吻合较好;液膜无量纲厚度达到13以后,液相密度将趋于稳定,两侧界面分子不会相互影响;分子动力学步长不影响平衡后的系统密度,但对表面张力的计算影响较明显.

The influence of simulation box parameters on molecular dynamics simulation of liquid-vapor system

In order to explore the influences of simulation box parameters which were long-ignored in the past on molecular dynamics simulation, the liquid-vapor coexistence system with 1000 molecules was simulated by Verlet-List searching method and Leapfrog difference algorithm. Liquid-vapor density and surface tension changes at 100K with number of system slices, vapor space size, film thickness and time step length were obtained. The results show that the number of system slices does not affect surface tension and density of two-phase. When z-axis dimensionless space size of system is equal to 60, the analog result is consistent with the experimental value. Liquid density gets steady and molecules in both sides of the interface will not affect each other while liquid film dimensionless thickness is greater than or equal to 13. Molecular dynamics time step length will not affect the density of system after the equilibrium, but have an obvious impact on calculation of surface tension.