Lad Kirit N, Patel Margi K, Pratap Arun
Computational Condensed Matter Physics Laboratory, Department of Physics, Sardar Patel University, Vallabh Vidya Nagar-388120, Gujarat, India.
Condensed Matter Physics Laboratory, Applied Physics Department, Faculty of Technology & Engineering, The M. S. University of Baroda, Vadodara-390001, Gujarat, India.
Phys Rev E. 2022 Jun;105(6-1):064107. doi: 10.1103/PhysRevE.105.064107.
A microscopic theory of molecular motion in classical monatomic liquids, proposed by Glass and Rice [Phys. Rev. 176, 239 (1968)10.1103/PhysRev.176.239], is revisited and extended to incorporate the dynamic friction in the Brownian description of the atomic diffusion in a mean-time-dependent harmonic force field. A modified, non-Markovian Langevin equation is utilized to derive an equation of motion for the velocity autocorrelation function with time-dependent friction coefficient. Numerical solution of the equation gives an excellent account of the velocity autocorrelation function in Lennard-Jones liquids, liquid alkali, and transition metals over a broad range of density and temperature. Derivation of the equation of motion leads to a self-consistent expression for the time dependence of friction coefficient. Our results demonstrate that the nature of time dependence of the friction coefficient changes dramatically with the liquid density. At low and moderate densities, the dynamic friction decays exponentially whereas it increases exponentially at high liquid densities. Our findings provide an opportunity for a different outlook of the Brownian description of atomic dynamics in liquids.
格拉斯和赖斯[《物理评论》176, 239 (1968)10.1103/PhysRev.176.239]提出的经典单原子液体中分子运动的微观理论被重新审视并扩展，以纳入在随时间变化的平均谐力场中原子扩散的布朗描述中的动态摩擦。利用一个修正的非马尔可夫朗之万方程来推导具有随时间变化的摩擦系数的速度自相关函数的运动方程。该方程的数值解很好地解释了 Lennard-Jones 液体、液态碱金属和过渡金属在广泛的密度和温度范围内的速度自相关函数。运动方程的推导得出了摩擦系数随时间变化的自洽表达式。我们的结果表明，摩擦系数随时间变化的性质随液体密度而显著变化。在低密度和中等密度下，动态摩擦呈指数衰减，而在高液体密度下呈指数增加。我们的发现为液体中原子动力学的布朗描述提供了一个不同的视角。
