朗之万方程在布朗运动数值模拟中的时间尺度分析

Time Scale Analysis of the Langevin Equation in Brownian Motion Numerical Simulations

从朗之万方程出发,比较了朗之万动力学(LD)和布朗动力学(BD)在布朗运动模拟中不同时间步长的选取对运动轨迹的影响.朗之万方程把大量流体分子对布朗颗粒的撞击等效成一项随机作用力,是一种热力学统计平均的处理方式,适用于在较大时间尺度下物理量的观测.模拟结果表明,时间步长并不影响BD模拟结果,而对LD的轨迹有着重要的影响.

Based on the Langevin equation,the trajectory of Langevin dynamics（ LD） and Brownian dynamics（ BD）simulationss at different timestep lenths are compared. The Langevin equation considers numerous collisions of fluid molecules on the Brownian particles as a stochastic force. It is a treatment for thermodynamics based on statistical average,which applies to the observation of physical quantity in large scale. The results show that the time step has profound effects on the LD trajectory,while little on the BD simulations.