Verdaguer A, Padro JA
Departament de Fisica Fonamental, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Jul;62(1 Pt A):532-7. doi: 10.1103/physreve.62.532.
Time correlation functions between the velocity of a tagged particle and velocities of particles within specified ranges of initial separations have been obtained by molecular dynamics simulation. These correlation functions have allowed us to analyze the momentum transfer between particles in different coordination shells. Two simple liquids at very different densities and two purely repulsive potentials with very different softnesses have been considered. The longitudinal correlations, which are the velocity cross-correlations along the initial direction defined by the centers of two given particles, have been calculated separately. It has been proven that these correlations should be attributed to particles both in front of and behind the central one. As with propagating longitudinal modes, they are strongly dependent on the softness of the potential core. Some characteristic features of the velocity correlation functions after the initial rise should be related to nonlongitudinal correlations. It has been shown that velocity cross-correlations between distinct particles cannot only be attributed to the direct interactions among particles, but also to the motions induced by the movement of a tagged particle on their neighbors.
通过分子动力学模拟获得了标记粒子的速度与初始间距在特定范围内的粒子速度之间的时间关联函数。这些关联函数使我们能够分析不同配位壳层中粒子之间的动量转移。我们考虑了两种密度差异很大的简单液体以及两种柔软度差异很大的纯排斥势。纵向关联，即沿着由两个给定粒子中心定义的初始方向的速度交叉关联，已分别计算。已经证明，这些关联应归因于中心粒子前后的粒子。与传播的纵向模式一样，它们强烈依赖于势核的柔软度。初始上升后速度关联函数的一些特征应与非纵向关联有关。已经表明，不同粒子之间的速度交叉关联不仅可归因于粒子之间的直接相互作用，还可归因于标记粒子在其邻居上的运动所引起的运动。
