Dynamic relaxation of a liquid cavity under amorphous boundary conditions.
Dynamic relaxation of a liquid cavity under amorphous boundary conditions.
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DOI：
10.1063/1.4720477
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发表时间：
2010-06
期刊：
影响因子：
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通讯作者：
A. Cavagna;T. Grigera;P. Verrocchio
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文献类型：
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作者：
A. Cavagna;T. Grigera;P. Verrocchio
亚当和吉布斯很久以前就用合作重排区域的增长来解释玻璃形成液体的减慢。然而，由于缺乏对增长顺序本质的了解，使得适当相关函数的定义变得复杂。一种选择是点到集（PTS）相关函数，它测量非晶边界条件对受限系统影响的空间跨度。通过使用交换蒙特卡罗算法，我们测量了低温下玻璃形成体模型中受非晶边界条件限制的液滴的平衡时间，并且我们表明，空腔弛豫时间随着液滴尺寸的增加而增加，当液滴增长超过点到集相关长度时，腔弛豫时间饱和到体积值。这一事实支持了这样的观点：点到集相关长度是协作重排区域的自然大小。另一方面，通过标准的非交换动力学计算的腔弛豫时间具有相反的行为，当腔尺寸减小时，腔弛豫时间显示出非常陡峭的增加。我们试图通过讨论模式耦合理论和激活过程之间可能的混合，并引入一种新型非晶态边界条件来调和这种差异，其灵感来自于冻结外部状态概念，作为常用冻结外部配置的替代品。
The growth of cooperatively rearranging regions was invoked long ago by Adam and Gibbs to explain the slowing down of glass-forming liquids. The lack of knowledge about the nature of the growing order, though, complicates the definition of an appropriate correlation function. One option is the point-to-set (PTS) correlation function, which measures the spatial span of the influence of amorphous boundary conditions on a confined system. By using a swap Monte Carlo algorithm we measure the equilibration time of a liquid droplet bounded by amorphous boundary conditions in a model glass-former at low temperature, and we show that the cavity relaxation time increases with the size of the droplet, saturating to the bulk value when the droplet outgrows the point-to-set correlation length. This fact supports the idea that the point-to-set correlation length is the natural size of the cooperatively rearranging regions. On the other hand, the cavity relaxation time computed by a standard, nonswap dynamics, has the opposite behavior, showing a very steep increase when the cavity size is decreased. We try to reconcile this difference by discussing the possible hybridization between mode-coupling theory and activated processes, and by introducing a new kind of amorphous boundary conditions, inspired by the concept of frozen external state as an alternative to the commonly used frozen external configuration.