Jiang S Q, Li M Z
Department of Physics, Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-Nano Devices, Renmin University of China, Beijing 100872, People's Republic of China.
J Phys Condens Matter. 2021 Apr 27;33(20). doi: 10.1088/1361-648X/abf271.
A new tetrahedral structure model was developed for disordered sphere packings, including not only regular tetrahedron (T), but also quartoctahedron (Q) and bcc simplex (B), the tetrahedral building blocks in fcc, hcp and bcc crystal structures, respectively. Both geometric frustrated configurations and local configurations associated with crystalline order in disordered packings can be comprehensively characterized. It is found that with increasing packing fraction, the population of T, Q, and B increases. Moreover, the crystal-type local configurations formed by face-adjacent T, Q and B increases as packing fraction increases, which is more prevalent than the geometric frustrated ones formed by face-adjacent T. In addition, as packing fraction increases, the local density of irregular simplexes is found to increase more quickly than regular ones, playing more important roles in the density increase in disordered packings. These structure features are found to be intrinsic in the jammed random sphere packings with different friction coefficients, which is independent of interparticle friction and only determined by the packing fraction. Our findings provide new understanding for the structural nature of disordered packings and the underlying structural basis of the random close packing.
针对无序球体堆积开发了一种新的四面体结构模型，其中不仅包括规则四面体（T），还包括四角八面体（Q）和体心立方单形（B），它们分别是面心立方、六方密堆积和体心立方晶体结构中的四面体构建单元。无序堆积中与晶体有序相关的几何受挫构型和局部构型都可以得到全面表征。研究发现，随着堆积分数的增加，T、Q和B的数量增加。此外，由面相邻的T、Q和B形成的晶体型局部构型随着堆积分数的增加而增加，这比由面相邻的T形成的几何受挫构型更为普遍。另外，随着堆积分数的增加，发现不规则单形的局部密度比规则单形增加得更快，在无序堆积的密度增加中起更重要的作用。这些结构特征在具有不同摩擦系数的堵塞随机球体堆积中是固有的，它与颗粒间摩擦无关，仅由堆积分数决定。我们的发现为无序堆积的结构性质以及随机密堆积的潜在结构基础提供了新的认识。
