论文标题
布朗运动与时间相关的摩擦和液体中的单粒子动力学
Brownian motion with time-dependent friction and single-particle dynamics in liquids
论文作者
论文摘要
玻璃和大米提出的经典美色液体液体中分子运动的微观理论[Phy。修订版176，239（1968）]进行了重新访问并扩展，以将动态摩擦纳入布朗对原子扩散的描述中，以平均时间依赖于时间依赖性的谐波力场。修改的非马克维亚兰格文方程用于推导速度自相关函数的运动方程，并具有时间依赖性的摩擦系数。该方程的数值解关于LJ液体，液体碱和过渡金属的速度自相关函数的良好说明，其密度和温度范围很大。运动方程的推导导致摩擦系数时间依赖性的自洽表达。我们的结果表明，摩擦系数的时间依赖性的性质随液体密度发生了巨大变化。在低和中等的密度下，动态摩擦呈指数衰减，而在高液体密度下它则指数增加。我们的发现提供了一个机会，可以使布朗对液体中原子动力学的描述有了新的前景。
A microscopic theory of molecular motion in classical monatomic liquids, proposed by Glass and Rice [Phy. Rev. 176, 239 (1968)], 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 LJ 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 to have a new outlook of the Brownian description of atomic dynamics in liquids.
