Scheiner Brett, Baalrud Scott D
Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52240, USA.
J Chem Phys. 2020 May 7;152(17):174102. doi: 10.1063/5.0005435.
A new kinetic-theory-based calculation of the self-diffusion coefficient for dense supercritical Lennard-Jones fluids is presented. The mean force kinetic theory, which was recently developed for transport in dense plasmas, is applied for the calculation of diffusion in dense neutral fluids. The calculation only requires the pair distribution function, a quantity that is readily calculable from equilibrium statistical mechanics for many systems, including the Lennard-Jones fluid. The self-diffusion coefficients are compared with calculations from molecular dynamics simulations, and good agreement at high density is demonstrated, even in the vicinity of the solid-fluid coexistence line. A comparison of different kinetic models with molecular dynamics simulations demonstrates that the transport coefficients have important contributions due to particle interaction via a potential of mean force and local correlations, which increase the collision rate. The new calculations compare well to those from free-volume theory and overcome a limitation of this theory that prevents its use in systems that interact via long range monotonic potentials. It is expected that this approach will also apply to other systems, including neutral-plasma and neutral-electrolyte mixtures.
提出了一种基于动力学理论的致密超临界 Lennard-Jones 流体自扩散系数的新计算方法。最近为致密等离子体中的输运而发展的平均力动力学理论，被应用于计算致密中性流体中的扩散。该计算仅需要对分布函数，对于许多系统，包括 Lennard-Jones 流体，这是一个可从平衡统计力学轻松计算的量。将自扩散系数与分子动力学模拟的计算结果进行了比较，结果表明在高密度下，甚至在固液共存线附近，二者吻合良好。不同动力学模型与分子动力学模拟的比较表明，由于通过平均力势和局部相关性的粒子相互作用，输运系数有重要贡献，这增加了碰撞率。新的计算结果与自由体积理论的计算结果比较良好，并且克服了该理论的一个局限性，即它不能用于通过长程单调势相互作用的系统。预计这种方法也将适用于其他系统，包括中性等离子体和中性电解质混合物。
