International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Sci Rep. 2017 Jan 6;7:39938. doi: 10.1038/srep39938.
In many glass-forming liquids, fractional Stokes-Einstein relation (SER) is observed above the glass transition temperature. However, the origin of such phenomenon remains elusive. Using molecular dynamics simulations, we investigate the break- down of SER and the onset of fractional SER in a model of metallic glass-forming liquid. We find that SER breaks down when the size of the largest cluster consisting of trapped atoms starts to increase sharply at which the largest cluster spans half of the simulations box along one direction, and the fractional SER starts to follows when the largest cluster percolates the entire system and forms 3-dimentional network structures. Further analysis based on the percolation theory also confirms that percolation occurs at the onset of the fractional SER. Our results directly link the breakdown of the SER with structure inhomogeneity and onset of the fraction SER with percolation of largest clusters, thus provide a possible picture for the break- down of SER and onset of fractional SER in glass-forming liquids, which is is important for the understanding of the dynamic properties in glass-forming liquids.
在许多玻璃形成液体中，分数斯泰克-爱因斯坦关系（SER）在玻璃化转变温度以上被观察到。然而，这种现象的起源仍然难以捉摸。使用分子动力学模拟，我们研究了模型金属玻璃形成液体中 SER 的破坏和分数 SER 的开始。我们发现，当由被困原子组成的最大簇的大小开始急剧增加时，SER 就会被破坏，此时最大簇沿着一个方向跨越了模拟盒的一半，并且当最大簇渗透整个系统并形成三维网络结构时，分数 SER 就会开始遵循。基于渗流理论的进一步分析也证实了，在分数 SER 开始时发生了渗流。我们的结果直接将 SER 的破坏与结构非均质性联系起来，分数 SER 的开始与最大簇的渗流联系起来，从而为玻璃形成液体中 SER 的破坏和分数 SER 的开始提供了一个可能的图景，这对于理解玻璃形成液体的动力学性质很重要。
