Local structure controls the nonaffine shear and bulk moduli of disordered solids
Local structure controls the nonaffine shear and bulk moduli of disordered solids
复制标题
局部结构控制无序固体的非仿射剪切和体积模量
作者：
M. Schlegel;J. Brujic;E. Terentjev;A. Zaccone
聚合模型系统，用于研究物质的力学响应，是随机网络的点原子，随机球形填料，或简单的晶体晶格；所有这些模型都假定粒子/原子之间存在中心力相互作用。每种模型在空间排列和粒子之间的相关性上都有所不同。反过来，这反映在剪切(G)和压缩(K)弹性模量的广泛不同的行为。编码为G、K及其比值的宏观弹性与微观晶格结构/有序之间的关系尚不清楚。我们提供了具有不同内部微观结构的模型非晶固体的局部取向顺序与弹性之间的定量分析联系，重点关注了两个相反的极限：填料（强排斥体积）和网络（无排斥体积）。理论预测，在填料中，由于排除体积的局部取向顺序在压缩下比在剪切下导致更少的非亲和性（更少的柔软性或更大的刚度）。这导致G/K值较低，这是一个有充分证据的现象，但缺乏微观解释。该理论还提供了一个很好的单参数描述的弹性压缩乳剂与实验数据相比，在广泛的填料分数范围。
Paradigmatic model systems, which are used to study the mechanical response of matter, are random networks of point-atoms, random sphere packings, or simple crystal lattices; all of these models assume central-force interactions between particles/atoms. Each of these models differs in the spatial arrangement and the correlations among particles. In turn, this is reflected in the widely different behaviours of the shear (G) and compression (K) elastic moduli. The relation between the macroscopic elasticity as encoded in G, K and their ratio and the microscopic lattice structure/order, is not understood. We provide a quantitative analytical connection between the local orientational order and the elasticity in model amorphous solids with different internal microstructure, focusing on the two opposite limits of packings (strong excluded-volume) and networks (no excluded-volume). The theory predicts that, in packings, the local orientational order due to excluded-volume causes less nonaffinity (less softness or larger stiffness) under compression than under shear. This leads to lower values of G/K, a well-documented phenomenon which was lacking a microscopic explanation. The theory also provides an excellent one-parameter description of the elasticity of compressed emulsions in comparison with experimental data over a broad range of packing fractions.