Mechanical properties of penta-graphene, hydrogenated penta-graphene, and penta-CN2 sheets

The present work investigates through reactive molecular dynamics simulations the mechanical properties of penta-graphene (PG), hydrogenated PG (HPG), and penta-CN2 at 300, 500, 700, and 900 K. Results reveal the higher temperature, the easier and faster transition under tension of PG to a structure, which is similar to a defective graphene. When increasing temperature from 300 to 900 K, the Young's modulus of PG reduces by 10%, but its yield stress (maximal tensile stress in the first stage before transition) and yield strain decrease considerably. The yield strain and yield in-plane stress of PG are about 10.75% and 3%; and 22.4 N/m and 7.9 N/m at 300 and 900 K, respectively. In the second stage with transition, the axial tensile stress increases, reaches a maximal value then decreases slowly. The maximal in plane stress of PG in the second stage falls within 17-20 N/m when temperature varies in the range of 300-900 K, and the strain at this maximal stress is 40.2, 35.0, 35.4 and 35.6% at 300, 500, 700, and 900 K, respectively. The mechanical properties of HPG and penta-CN2 sheets decrease slightly with an increase of temperature. Hydrogenation reduces the Young's modulus of PG by 25-28%, but increases the maximal tensile stress because HPG does not undergo phase transformation under tension, while PG does. Among three examined sheets, the penta-CN2 sheet exhibits the highest Young's modulus, but the lowest tensile strength and fracture strain. At 300 K, the two-dimensional (2D) Young's modulus, 2D tensile strength and strain at tensile strength of HPG and penta-CN2 sheets are 210 and 314 N/m; 28.7 and 14.4 N/m; and 19.6 and 9.6%, respectively. (C) 2017 Elsevier B.V. All rights reserved.