Oppelstrup T, Dzugutov M
Department of Numerical Analysis and Computer Science, Royal Institute of Technology, S-100 44 Stockholm, Sweden.
J Chem Phys. 2009 Jul 28;131(4):044510. doi: 10.1063/1.3184850.
A statistical analysis of the geometries of particle trajectories in the supercooled liquid state is reported. The analysis we present here is based on the statistics of the first-passage trajectory length. We examine two structurally different fragile glass-forming liquids simulated by molecular dynamics. In both liquids, the trajectories are found to reveal three distinct diffusion regimes. A short-range confinement to the cage of nearest neighbors is followed by a persistent diffusion regime. At a still larger spatial scale, the particle trajectories demonstrate a novel diffusion anomaly: a long-range localization distinct from the short-range localization. This phenomenon can be interpreted in terms of the potential-energy landscape topography with the local energy minima coalescing into metabasins--compact domains with low escape probability. We also demonstrate that the persistent diffusion regime can be linked to the exponential decay of the self-part of the van Hove correlation function.
报道了对过冷液态中粒子轨迹几何形状的统计分析。我们在此呈现的分析基于首次通过轨迹长度的统计。我们研究了通过分子动力学模拟的两种结构不同的易脆玻璃形成液体。在这两种液体中，轨迹都显示出三种不同的扩散状态。先是在最近邻粒子构成的笼中进行短程限制，接着是持续扩散状态。在更大的空间尺度上，粒子轨迹呈现出一种新的扩散异常：一种与短程局域化不同的长程局域化。这种现象可以根据势能景观地形来解释，其中局部能量最小值合并成亚盆地——具有低逃逸概率的紧凑区域。我们还证明，持续扩散状态可以与范霍夫关联函数自部分的指数衰减联系起来。
