Competing Hexagonal and Square Lattices on a Spherical Surface.

The structural properties of packed soft-core particles provide a platform to understand the cross-pollinated physical concepts in solid-state and soft-matter physics. Confined on a spherical surface, the traditional differential geometry also dictates the overall defect properties in otherwise regular crystal lattices. Using molecular dynamics simulation of the Hertzian model as a tool, we report here the emergence of new types of disclination patterns: domain and counter-domain defects, when hexagonal and square patterns coexist. A new angle is presented to understand the incompatibility between tiling lattice shapes and the available spherical areal shapes, which is common in nature─from molecular systems in biology to backbone construction in architectures.