Graphyne-type nano-metamaterials: A comprehensive molecular dynamics simulation

Abstract

With advances in nanotechnology, the search for novel and nontraditional materials beyond the already known nanostructures such as graphene and graphynes is rising. Recently, a graphyne-like nanostructure with the directional alignment of the acetylenic linkages, the so-called directional graphyne, as an interesting class of nano-metamaterials has been proposed which possesses fascinating physical properties. In this study, the mechanical behavior of the directional graphynes is investigated using molecular dynamics simulation. The effects of temperature, loading direction, and number of acetylenic bonds on the elastic and fracture properties are examined. Comparisons between the mechanical characteristics of the directional graphynes and those of the graphene and graphynes are also provided. The results reveal a high degree of anisotropy in Young's modulus and Poisson's ratio for the directional graphynes compared to the graphene and graphynes. However, the shear modulus is found to be insensitive to the loading direction for all three nanostructures. On the other hand, they all exhibit significant anisotropic fracture properties. An exception is observed for the fracture strain of the directional graphynes under shear loading. The failure mechanisms of the graphynes and directional graphynes are found to be different when the tensile loading is in the zigzag direction. Also, the results indicate that the directional graphynes exhibit interesting and different wrinkle behavior, and especially those with longer acetylenic linkages, are very flexible nanostructures under shear loadings.