Collective intermolecular motions dominate the picosecond dynamics of short polymer chains.
Collective intermolecular motions dominate the picosecond dynamics of short polymer chains.
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集体分子间运动主导短聚合物链的皮秒动力学
DOI：
10.1103/physrevlett.111.173003
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发表时间：
2013
影响因子：
8.6
通讯作者：
中科院分区：
文献类型：
--
作者：
利用中子散射和广泛的分子动力学方法模拟了一个全原子系统，研究了导致质心自扩散的短时动力学过程。模拟的动力学与分辨率分辨的飞行时间准弹性中子散射非常一致。异常亚扩散质心运动可以通过明确地解释粘弹性流体动力学相互作用来模拟。无模型分析的分子骨架的局部重取向揭示了三个松弛过程：而两个松弛表征局部键旋转和全球分子重取向，中间时间的第三个组件可以归因于瞬态的流动状运动的原子在不同的分子。这些集体运动的存在，在这封信中清楚地可视化，强烈有助于分子液体中的链弛豫。
Neutron scattering and extensive molecular dynamics simulations of an all atomsystem were performed to address the short-time dynamics leading to center-of-mass self-diffusion. The simulated dynamics are in excellent agreement with resolution resolved time-of-flight quasielastic neutron scattering. The anomalous subdiffusive center-of-mass motion could be modeled by explicitly accounting for viscoelastic hydrodynamic interactions. A model-free analysis of the local reorientations of the molecular backbone revealed three relaxation processes: While two relaxations characterize local bond rotation and global molecular reorientation, the third component on intermediate times could be attributed to transient flowlike motions of atoms on different molecules. The existence of these collective motions, which are clearly visualized in this Letter, strongly contribute to the chain relaxations in molecular liquids.