Nanoindentation Models And Mechanical Properties Of Graphene And Graphyne: A Molecular Dynamics Study

Graphene, a nanometer material consisting of an atomic layer with the sp2 hybridization arranged in the plane of hexagonal honeycomb lattice, has been identified as the promising material to overcome the limitations on the basis of silicon nanotechnology. It is believed that graphene has great application as the aspect of quantum dot, nanoconstrictions, spin valve devices, light-emitting electrochemical cell, solar batteries, semiconductor materials and nanocompostion attributes to its excellent optical, electrical, magnetic and mechanical properties. In the typical progress, we investigate the mechanical properties of perfect and defect graphene corresponding to nanoindentation models by classical molecular dynamics method. The main points of our present work are as follows:(1) Nanoindentaion models calculations based on the molecular dynamics method are performed to study the mechanical properties of multilayer graphene. In the typical progress, sectional fittings were made in small and large defection scopes. Results reveal that the Young’s modulus of graphene is not consistent under different strain scopes, with the value being much larger in small defection scopes.(2) We investigate the influence of different size of membranes, indenters and pre-tension on the determination of Young’s modulus using nanoindentation models. The value of Young’s modulus for 1-5 layers was estimated to be 1.00 TPa. The value of Young’s modulus starts to increase slightly after five atomic layers, indicating the dependence of Young’s modulus on the thickness of the carbon layers. The change of pre-tension is well self-consistent with the fact that the Young’s modulus is greater than five layers of graphene.(3) We investigate the effect of temperature and stack patterns on the determination of Young’s modulus. The Young’s modulus shows almost a linear behavior with temperature in the range of 300 K-1000 K, with the value being larger at higher temperatures. This phenomenon is attributes to the anharmonicity. The Young’s modulus of multilayer graphene is almost consistent under different order of stack modes, which confirms that the stack modes have weak effect on the Young’s modulus of multilayer graphene.(4) We investigate the different defects on the determination of Young’s modulus of monolayer grapheme. This study mainly addresses the point, vacancy and Stone-Wales defect. The defects has obvious effect on the Young’s modulus of grapheme, which the lower concentration decrease the mechanical properties of graphene. The strength of graphene not only has a strong dependence on the size of defect but also corresponding to the angle of grain boundary.(5) The nanoindentation of graphyne for the first time has been studied in the light of molecular dynamics method, which is a novel two-dimensional carbon material. Results reveal that the Young’s modulus is approximately half of that of graphene. Graphyne is softer than graphene. The Young’s modulus of graphyne is insensitive to temperature. The mechanical properties of graphyne have weaker resistance with regard to the increase of temperature compared with graphene.