MOLECULAR-DYNAMICS ALGORITHMS AND HYDRODYNAMIC SCREENING
MOLECULAR-DYNAMICS ALGORITHMS AND HYDRODYNAMIC SCREENING
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DOI：
10.1063/1.465444
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发表时间：
1993-11-01
影响因子：
4.4
通讯作者：
DUNWEG, B
中科院分区：
文献类型：
--
作者：
DUNWEG, B
本文考虑了布朗粒子系统在显式溶剂粒子浴中的分子动力学模拟。广义算法（朗之万模拟），其中布朗粒子和溶剂粒子人工耦合到一个热浴，分析其动力学性质的长尺度。虽然这样的动力学显然是非物理的，但它的分析是有用的，原因有二：朗之万算法经常以特别的方式应用，并且通过选择足够弱的耦合到热浴，它的动力学性质与物理哈密顿量的偏差可以任意小。Mori-Zwanzig投影算子形式主义的直接应用表明，违反全球动量守恒的结果在人工筛选的水动力相互作用，与筛选长度成正比的算法的摩擦常数的平方根倒数。其结果在形式上类似于半稀释聚合物溶液中流体力学筛选的唯象理论中给出的表达式。
In this paper molecular dynamics simulations of a system of Brownian particles in an explicit bath of solvent particles are considered. Generalized algorithms (Langevin simulations), in which both the Brownian particles and the solvent particles are artificially coupled to a heat bath, are analyzed for their dynamical properties on long length scales. Although such a dynamic is clearly unphysical, its analysis is useful for two reasons: The Langevin algorithm is frequently applied in an ad hoc fashion, and the deviation of its dynamical properties from the physical Hamiltonian case can be made arbitrarily small by choosing a sufficiently weak coupling to the heat bath. By a direct application of the Mori-Zwanzig projection operator formalism it is shown that the violation of global momentum conservation results in an artificial screening of the hydrodynamic interactions, with a screening length proportional to the inverse square root of the friction constant of the algorithm. The result is formally similar to expressions given in phenomenological theories of hydrodynamic screening in semidilute polymer solutions.