Laghaei Rozita, Eskandari Nasrabad Afshin, Eu Byung Chan
Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 2K6, Canada.
J Phys Chem B. 2005 Nov 17;109(45):21375-9. doi: 10.1021/jp050504p.
In this paper, we apply the Matteoli-Mansoori empirical formula for the pair correlation function of simple fluids obeying the Lennard-Jones potential to calculate reduced self-diffusion coefficients on the basis of the modified free volume theory. The self-diffusion coefficient thus computed as functions of temperature and density is compared with the molecular dynamics simulation data and the self-diffusion coefficient obtained by the modified free volume theory implemented with the Monte Carlo simulation method for the pair correlation function. We show that the Matteoli-Mansoori empirical formula yields sufficiently accurate self-diffusion coefficients in the supercritical regime, provided that the minimum free volume activating diffusion is estimated with the classical turning point of binary collision at the mean relative kinetic energy 3k(B)T/2, where k(B) is the Boltzmann constant and T is the temperature. In the subcritical regime, the empirical formula yields qualitatively correct, but lower values for the self-diffusion coefficients compared with computer simulation values and those from the modified free volume theory implemented with the Monte Carlo simulations for the pair correlation function. However, with a slightly modified critical free volume, the results can be made quite acceptable.
在本文中，我们应用适用于服从 Lennard-Jones 势的简单流体对关联函数的 Matteoli-Mansoori 经验公式，基于修正的自由体积理论计算约化自扩散系数。将如此计算得到的作为温度和密度函数的自扩散系数，与分子动力学模拟数据以及通过用蒙特卡罗模拟方法实现的对关联函数的修正自由体积理论所获得的自扩散系数进行比较。我们表明，Matteoli-Mansoori 经验公式在超临界区域能给出足够精确的自扩散系数，条件是激活扩散的最小自由体积用平均相对动能为 3k(B)T/2 时二元碰撞的经典转折点来估计，其中 k(B) 是玻尔兹曼常数，T 是温度。在亚临界区域，与计算机模拟值以及通过用蒙特卡罗模拟对关联函数实现的修正自由体积理论得到的值相比，该经验公式给出的自扩散系数在定性上是正确的，但数值较低。然而，通过对临界自由体积进行略微修正，结果可以变得相当令人满意。
