Jin Yuliang, Yoshino Hajime
Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China;
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Proc Natl Acad Sci U S A. 2021 Apr 6;118(14). doi: 10.1073/pnas.2021794118.
The concept of jamming has attracted great research interest due to its broad relevance in soft-matter, such as liquids, glasses, colloids, foams, and granular materials, and its deep connection to sphere packing and optimization problems. Here, we show that the domain of amorphous jammed states of frictionless spheres can be significantly extended, from the well-known jamming-point at a fixed density, to a jamming-plane that spans the density and shear strain axes. We explore the jamming-plane, via athermal and thermal simulations of compression and shear jamming, with initial equilibrium configurations prepared by an efficient swap algorithm. The jamming-plane can be divided into reversible-jamming and irreversible-jamming regimes, based on the reversibility of the route from the initial configuration to jamming. Our results suggest that the irreversible-jamming behavior reflects an escape from the metastable glass basin to which the initial configuration belongs to or the absence of such basins. All jammed states, either compression- or shear-jammed, are isostatic and exhibit jamming criticality of the same universality class. However, the anisotropy of contact networks nontrivially depends on the jamming density and strain. Among all state points on the jamming-plane, the jamming-point is a unique one with the minimum jamming density and the maximum randomness. For crystalline packings, the jamming-plane shrinks into a single shear jamming-line that is independent of initial configurations. Our study paves the way for solving the long-standing random close-packing problem and provides a more complete framework to understand jamming.
由于堵塞概念在软物质（如液体、玻璃、胶体、泡沫和颗粒材料）中具有广泛的相关性，并且与球体堆积和优化问题有着深刻的联系，因此吸引了大量的研究兴趣。在这里，我们表明无摩擦球体的非晶态堵塞状态的范围可以显著扩展，从固定密度下的著名堵塞点，扩展到跨越密度和剪切应变轴的堵塞平面。我们通过压缩和剪切堵塞的无热和热模拟来探索堵塞平面，初始平衡构型由一种高效的交换算法制备。基于从初始构型到堵塞的路径的可逆性，堵塞平面可以分为可逆堵塞和不可逆堵塞区域。我们的结果表明，不可逆堵塞行为反映了从初始构型所属的亚稳玻璃盆地的逃逸或不存在这样的盆地。所有堵塞状态，无论是压缩堵塞还是剪切堵塞，都是等静压的，并且表现出相同普适类的堵塞临界性。然而，接触网络的各向异性非平凡地取决于堵塞密度和应变。在堵塞平面上的所有状态点中，堵塞点是具有最小堵塞密度和最大随机性的唯一一点。对于晶体堆积，堵塞平面收缩为一条独立于初始构型的单一剪切堵塞线。我们的研究为解决长期存在的随机密堆积问题铺平了道路，并提供了一个更完整的框架来理解堵塞。
