Lennard-Jones简单流体的自扩散系数与密度的依赖性研究  

Density Dependence of the Self-Diffusion Coefficient of Lennard-Jones Simple Fluid

作　　者：赵晨辰 杨晓峰[1] ZHAO Chenchen;YANG Xiaofeng(School of Semiconductor and Physics,North University of China,Taiyuan 030051,China)

机构地区：[1]中北大学半导体与物理学院,山西太原030051

出　　处：《中北大学学报（自然科学版）》2023年第4期346-351,共6页Journal of North University of China(Natural Science Edition)

摘　　要：基于平衡分子动力学模拟(EMD)的方法计算了Lennard-Jones(LJ)流体的自扩散系数。结合维里定理和能量均分定理分析了体系温度和密度对扩散的影响,并通过分子动力学模拟进行了验证。研究结果表明:原子的有效直径随温度的升高而减小,进而使自扩散系数与温度的2/3次方成正比;在中等温度部分,扩散系数大体上随密度的升高而减小。本文给出了流体自扩散系数与密度依赖关系的具体函数形式,这一函数在约化温度高于1.33,约化分子数密度为0.1194~1.1942的范围内可准确描述LJ流体的自扩散行为;如果约化密度大于1.298,原子扩散行为停止,LJ流体发生玻璃化改变。The self-diffusion coefficient of Lennard-Jones(LJ)fluid was calculated based on the equilibrium molecular dynamics(EMD)simulation method.The effects of temperature and density on diffusion were analyzed by combining Virial theorem and energy equipartition theorem,and the theoretical analysis was verified by simulation results.The results indicate that the effective diameter of fluid particle decreases as the temperature increases,so the self-diffusion coefficient is proportional to the two-thirds power of the temperature.In the middle temperature,the diffusion coefficient decreases with the increase of density.In this paper,the specific function form of the dependence between fluid self-diffusion coefficient and density is given.This formula can accurately describe the self-diffusion behavior of LJ fluid when the reduced temperature is greater than 1.33 and the reduced number density in the range from 0.1194 to 1.1942.If the reduced density is greater than 1.298,the atomic diffusion behavior stops and the LJ fluid undergoes a glass transition.

关 键 词：Enskog理论 Lennard-Jones流体 自扩散系数 分子动力学 

分 类 号：O641[理学—物理化学]