Mechanical behaviours of penta-graphene and effects of hydrogenation

A new graphene allotrope, penta-graphene (PG), has been proposed recently with unique electronic properties. However, the mechanical behaviors have not been fully explored yet. In this work, we performed classic molecular dynamics (MD) simulations to evaluate the fundamental mechanical properties of PG under uniaxial tension. The effects of strain rate and hydrogenation on the mechanical properties and deformation mechanism of PG were also systematically investigated. Our simulations show that unlike brittle graphene, PG behaves plastically during tensile deformation, which is inherently originated from the irreversible pentagon-to-polygon structural transformation. Higher strain rate generally leads to lower Young's modulus but higher yield and ultimate strength and strain of PG. In addition, it is also found that fully hydrogenated PG (HPG) exhibits brittle fracture characteristics and does not undergo structural transformation under tension, while HPG with lower H-coverages possess similar mechanical behaviors to that of pristine PG. Moreover, we demonstrate that temperature can trigger pentagon-to-hexagon structural reconstruction for free-standing pristine PG and partially HPG, but cannot for fully HPG. These findings are expected to provide important guidelines for the practical applications of PG in nanodevices and nanoelectronics.