Investigation On The Mechanical Behaviors And Properties Tuning Of Penta-graphene

Over the past decade,numerous researches on low-dimensional allotropes and their derivatives of carbon have been carried out.Many of these materials have excellent physical,electronic and thermal properties and wide application prospects.Penta-graphene(PG)is a newly proposed two-dimensional metastable carbon allotrope composed entirely of carbon pentagons.The unique atomic configuration of PG makes it possess a negative Poisson’s ratio effect,ultra-high mechanical strength and quasidirect band gap.It has been reported that PG has tunable band gap,possesses excellent mechanical strength and thermal stability,and its thermal conductivity and electronic performance can be improved by functionalization.However,there are few investigations on the mechanical properties of PG and its influencing factors,which need to be supplemented.In this paper,the molecular dynamics simulation method was used to simulate the tensile deformation process of PG and functionalized pentagraphene,the internal deformation mechanism was analyzed.The main work is listed as follows:1.The mechanical properties of PG and the effect of strain rate and temperature on its mechanical properties were investigated.The simulation results show that unlike brittle graphene,PG exhibits plastic behavior during tension,which is inherently originated from the irreversible pentagon-to-polygon structural transformation.The mechanical parameters of PG such as yield stress and strain and Young’s modulus are lower than those of graphene.Higher strain rate generally leads to lower Young’s modulus but higher yield and ultimate strength and strain of PG.With the increase of strain rate,the process of carbon bond fracture and reorganization becomes shorter,local deformation increases and carbon rings transition decreases.The PG has a slightly lower melting point than graphene,and both temperature and load can trigger the transition of the pentagons to other rings.Uniaxial tensile tests at different temperatures show that the yield stress and strain and Young’s modulus of PG decrease with the increasing temperature.2.The effect of functionalization on the mechanical properties of pentagon graphene was investigated.The simulation results show that fully hydrogenated PG(HPG)exhibits brittle fracture characteristics and does not undergo structure transformation under tensile load,while HPGs with lower H-coverages possess similar mechanical behavior with that of pristine PG.PG that is functionalized by epoxy groups or hydroxyl groups exhibits brittle fracture and there is no carbon ring transition during tensile deformation.Hydrogenation,epoxidation and hydroxylation all increase the yield stress and strain of pentagonal graphene,but the Young’s modulus is reduced.