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arXiv 2108.04848cond-mat.soft
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约束对玻璃化转变的非单调效应

Non-monotonic effect of confinement on the glass transition

Fathollah Varnik, Thomas Franosch

摘要:

玻璃形成液体和它们的结构的松弛动力学的影响在附近的限制壁。考虑到这种效应在科学和工业领域中应用的巨大潜力,其中液体在强约束下发生(例如,随着纳米技术的发展,研究这种非单调行为的各个方面和后果的研究人员数量迅速增加。这篇评论的目的是提供一个概述的研究活动在这个新兴的领域。我们首先简要地讨论如何竞争机制,如包装效果和短程吸引力可能会导致在散装的非单调玻璃化转变的情况。然后,我们分析禁闭效应的流体动力学使用的热力学路线,涉及到单粒子动力学的过剩熵。此外,与Widom的插入概率的扩散动力学,振荡的局部动力学密度在中等密度相当好地描述。然而,在高密度属于过冷制度,这种方法打破了强烈的集体效应的发病信号。事实上,禁闭引入了一个新的长度尺度,在高密度和小孔径的限制竞争的流体的短程局部秩序。这引起了一个非单调依赖的包装结构上的限制,与相应的效果上的动态结构松弛。这种非单调效应也发生在锥板式通道的情况下,其中限制的程度随着距顶点的距离而变化。这是一个非常有前途的问题,为未来的研究揭示交替玻璃和液体状域的存在的可能性。

英文摘要:

The relaxation dynamics of glass forming liquids and their structure are influenced in the vicinity of confining walls. In view of the great potential of this effect for applications in those fields of science and industry, where liquids occur under strong confinement (e.g., nano-technology), the number of researchers studying various aspects and consequences of this non-monotonic behaviour has been rapidly growing. This review aims at providing an overview of the research activity in this newly emerging field. We first briefly discuss how competing mechanisms such as packing effects and short-range attraction may lead to a non-monotonic glass transition scenario in the bulk. We then analyse confinement effects on the dynamics of fluids using a thermodynamic route which relates the single particle dynamics to the excess entropy. Moreover, relating the diffusive dynamics to the Widom's insertion probability, the oscillations of the local dynamics with density at moderate densities are fairly well described. At high densities belonging to the supercooled regime, however, this approach breaks down signaling the onset of strongly collective effects. Indeed, confinement introduces a new length scale which in the limit of high densities and small pore sizes competes with the short-range local order of the fluid. This gives rise to a non-monotonic dependence of the packing structure on confinement, with a corresponding effect on the dynamics of structural relaxation. This non-monotonic effect occurs also in the case of a cone-plate type channel, where the degree of confinement varies with distance from the apex. This is a very promising issue for future research with the possibility of uncovering the existence of alternating glassy and liquid-like domains.

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