Elastic constants of graphane, graphyne, and graphdiyne

Abstract

Graphyne (two-dimensional one-atom-thick carbon allotrope) a promising semiconductor distinct by the number of acetylenic bonds. The study of mechanical properties is of key importance for electronics, composite fabrication, and fundamental understanding of the mechanical behavior of 2D structures. Molecular dynamics and analytical calculations were used to obtain the elastic constants (stiffness and compliance constants, Young’s and shear modulus, Poisson’s ratio) for five graphynes. For the first time, the direct link between stiffness and compliance constants for 2D materials were presented. Among hexagonal graphynes, γ1 has the largest Young’s modulus (154 N/m). The deformation is attributed to the competition between the rotation and elongation of bonds in graphyne under loading. An analysis of stationary and extreme values of Young’s and shear modulus, Poisson’s ratio was carried out for the first time based on the search for the extremum of a function of one variable. A strong mechanical anisotropy was observed for orthorhombic graphynes (β3 and γ2). Orthorhombic graphynes possess extremely large in-plane Poisson’s ratio. Explanation of how elastic constants depend on structure density and atomic arrangement was given. The obtained results open new opportunities for the development of new nanomechanical devices based on such 2D materials.