Local rotational symmetry in the packing of uniform spheres

• Published in: Physical chemistry chemical physics : PCCP 2017-06, Vol.19 (22), p.14588-14595
• Main Authors: Tian, Z. A, Dong, K. J, Yu, A. B
• Format: Article
• Language: English
• Subjects: Atomic structure; Crystals; Evolution; Face centered cubic lattice; Particle physics; Phase transformations; Physical chemistry; Symmetry
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp01152k

Local rotational symmetry (LRS) of a particulate system is important for understanding its structure and phase transition. However, how to properly characterize LRS for this system is still a challenge as the system normally includes both ordered and disordered local structures. Herein, based on the so-called common neighbour subcluster (CNS), we proposed a method to characterize the LRS of uniform spheres packings with the packing fraction ρ ranging within 0.20 and 0.74. It was found that different fold LRSs coexist in most packings, and their maximum degree increases at ρ < 0.64, except for the 2-fold LRS held by 6-sphere CNS that continuously increases to form the fcc crystal at ρ = 0.74. The overall LRS involving all the CNSs monotonically increases with two critical changes at ρ = (0.35-0.40) and 0.64; the evolution of individual LRSs held by specific CNS groups critically changes at ρ (0.35-0.40), 0.50, 0.55-0.60, and 0.64. The physics corresponding to these critical changes has also been discussed. The findings will significantly enrich the understanding of the structural symmetry of materials including atoms and particles. The significant changes of local rotational symmetry reveal the essential structural characteristic of sphere packings, especially at all the critical points.