A Brownian dynamics simulation method for analyzing particle behavior in nonuniform and alternating electric fields

A new iterative Brownian dynamics simulation (BDS) method for analyzing the diffusive behavior of particles in an alternating electric field is proposed and tested in comparison with several previous techniques, including the most widely used BDS method developed by Ermak. To evaluate the proposed method with other schemes, particle trajectories in constant, AC, nonuniform DC in DMA, and quadrupole electric fields were obtained from each algorithm with various integration time steps. It is shown that the proposed BDS method is much more accurate at predicting the mean and variance of particle position for most cases. With respect to algorithm efficiency, the new scheme is about 5-50 times more efficient than the conventional BDS method for high-frequency AC electric fields. The simulation results for a particle beam generated in a quadrupole electric field show that the selection of a suitable algorithm and the proper size of time step are important for calculating system properties related to the diffusive motion of particles. In addition, a correction to the stochastic term is suggested and its effect investigated. (c) 2006 Elsevier Ltd. All rights reserved.