Department of Physics "A. Pontremoli," University of Milan, 20133 Milan, Italy;
Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, United Kingdom.
Proc Natl Acad Sci U S A. 2020 Aug 18;117(33):19653-19655. doi: 10.1073/pnas.2010787117. Epub 2020 Aug 3.
Experimental observations of unexpected shear rigidity in confined liquids, on very low frequency scales on the order of 0.01 to 0.1 Hz, call into question our basic understanding of the elasticity of liquids and have posed a challenge to theoretical models of the liquid state ever since. Here we combine the nonaffine theory of lattice dynamics valid for disordered condensed matter systems with the Frenkel theory of the liquid state. The emerging framework shows that applying confinement to a liquid can effectively suppress the low-frequency modes that are responsible for nonaffine soft mechanical response, thus leading to an effective increase of the liquid shear rigidity. The theory successfully predicts the scaling law [Formula: see text] for the low-frequency shear modulus of liquids as a function of the confinement length L, in agreement with experimental results, and provides the basis for a more general description of the elasticity of liquids across different time and length scales.
在非常低的频率范围内（约为 0.01 到 0.1 Hz）对受限液体进行的意外剪切刚度的实验观察，使我们对液体弹性的基本理解产生了质疑，并对液体状态的理论模型提出了挑战。在这里，我们将适用于无序凝聚态物质系统的晶格动力学非仿射理论与液体的弗伦克尔理论相结合。新兴的框架表明，对液体施加限制可以有效地抑制低频模式，这些模式负责非仿射软机械响应，从而导致液体剪切刚度的有效增加。该理论成功地预测了液体低频剪切模量的标度律 [公式：见正文] 作为受限长度 L 的函数，与实验结果一致，并为在不同时间和长度尺度上更一般地描述液体弹性提供了基础。
