Wrinkling Behaviour of Annular Graphynes under Circular Shearing Load Using Molecular Dynamics Simulations

Graphyne, a novel carbon allotrope, is a two-dimensional lattice of sp2+sp1 hybridization-type carbon atoms, similar to graphene. The initiation and development of wrinkles in single-layer graphynes (α-, β-, γ-, and 6, 6, 12-graphyne) subjected to in-plane circular shearing are investigated. In comparison with graphene, wrinkle pattern and profile characterization in relation to wave number, wavelength and amplitude of graphynes are extensively explored using classic molecular-dynamics (MD) simulations. Unlike graphene, the wave numbers of graphynes increase with increasing rotational angles; the wavelengths reduce correspondingly. The amplitudes show an increasing trend, with some local drops when the rotational angles increase. The drops occur as the positions of the wave numbers increase. Graphynes have superior fracture properties to graphene, despite the densities of graphynes being far lower. The fracture rotational angles depend on the percentages of acetylenic linkages in the graphyne structures: the more acetylenic linkages, the larger the fracture rotational angles. Meanwhile, acetylenic linkages also affect the bond length strains of the graphynes during the wrinkling process. The influences of the temperature on the fracture rotational angles are also examined to obtain further insights into the mechanical properties of such kinds of carbon allotropes. The achieved results can be used as guidelines for the wrinkling control and potential applications of graphynes.