二元Lennard-Jones液体的相分离过程及其扩散性质的分子动力学研究

Molecular dynamics study of the phase separation and diffusion in Lennard-Jones binary liquid

采用分子动力学(MD)模拟方法,研究了二元体系中相分离过程、粒子的扩散系数以及相分离域尺寸大小随温度的变化规律.发现,相分离域随温度的生长过程可以分为两个阶段,分别是温度比较高的快速生长阶段和低温时的稳定生长阶段;相分离体系中系统的扩散激活能不是常数,而是一个随温度变化的函数,并且当温度高于60 K时,满足关系式E(T)=a+bTc.讨论了组元尺寸的变化对相分离过程的影响.结果表明,随两组元中某一组元尺寸σ的减小,系统的扩散性增加,粒子分离程度增强,使系统的相分离域更容易长大,促进系统相分离.

Molecular dynamics（MD） simulation is performed to study the diffusion and phase separation process in binary Lennard-Jones（LJ） liquid.It is found that the growth of phase separation with temperature can be divided into two stages.The first is the fast-growth at high temperatures and the second is the steady-growth at low temperatures.Diffusion activation energy in the phase separation system is not a constant,but a function of temperature and follows the relation of E=a＋bTc.The influence of the sizes of the components on the phase separation is also discussed.The results shows that the diffusivity increases when the component size decreases.This facilitates the phase separation.