一种描述金属界面原子扩散的加速分子动力学方法

传统分子动力学(MD)的纳秒级时间尺度限制了对固体界面原子的深层扩散、渗透以及相形成等长时动力学性质的模拟研究.在Voter的超动力学框架内，提出了一种更为简单的偏移势的构建方法.该方法通过在偏移势中引入一个加速因子，抬高了原势阱，从而加速了原子的跃迁，将MD模拟的时间尺度提高了若干个数量级.更为重要的是，该方法不需要预知体系势能的势阱及鞍点分布，还能够将原势能曲面的特性完全保留.以Mg/Zn界面扩散为例，选取简单的Lennard-Jones双体势，考察了不同加速因子对界面原子扩散速度的影响.结果显示，该 关键词： 超动力学 加速因子 原子扩散 金属界面

A method of accelerating molecular dynamics simulation for atomic diffusion in metallic interface

Many interesting long-time dynamic properties of solid interface, such as deep diffusion, pervasion and phase forming, cannot be simulated directly using traditional molecular dynamics (MD) because of nanosecond timescale limitations. Thus, a simpler bias potential form has been proposed within the Voter's hyper dynamics scheme. In this method, the potential energy wells are raised by adding a coefficient, which was defined as the accelerating factor, to the original potential. So, the escape rate from potential wells was enhanced, which extends the timescale by several orders of magnitude comparing to the traditional MD simulations. What's more important, the features of potential surface are reserved even without any in_advance knowledge of the location of either the potential energy wells or saddle points. We demonstrate this method by applying it to the mutual diffusion of atoms in Mg/Zn interface with different accelerating factors using a simple Lennard-Jones potential. The results showed that long-time MD simulation can be realized very easily by our approach.