Simulation Study On The Elastic-electro Coupling Mechanical Properties Of Graphene

Graphene has been widely cared by the whole science world since Novoselov et al. successfully detach it from graphite in2004. Many researches show that graphene has excellent electronical, thermal, magnetic and mechanical properties. It has great potential application in many fields, especially in high performance nanodevices, such as field effect transistors, sensors, and energy storages, such as fuel cells and battery. However, many researches on the mechanical properties of the graphene sheets have been conducted all over the world by experimental method and theoretical studies, the complicated coupling mechanical behavior and mechanism of graphene under the effect of mechanical load, thermal load and electric field are not discussed. And the researches about chiral and size dependence of the mechanical properties of graphene are still not enough. The mechanical, the elastic-electro coupling, the elastic-thermal-electro coupling properties and behavior of zigzag and armchair graphene has been investigated and chiral and size dependence of the mechanical properties of zigzag and armchair graphene are discussed by using the quantum mechanical dynamics and molecular dynamics method.Firstly, the mechanical behaviors of zigzag and armchair graphene under tensile and compressive loading have been simulated by quantum mechanical dynamics method based on the empirical potential function. The mechanical properties and fracture mechanism of zigzag and armchair graphene have been discussed. The results show the critical stresses of zigzag graphene under tensile and compressive loading are larger than that of armchair graphene. The influences of external load on the electronic properties of zigzag and armchair graphene have been also studied by the variation of Homo, Lumo and energy gap.Secondly, a modified atomistic moment method is proposed to obtain the distribution of electric charges on graphene which can describe the influences of the deformation based on classical electrostatics theory. The results are in good agreement with the results obtained by DFT (density function theory) method. The modified atomistic moment method costs less time. The electrostatic interactions between charged carbon atoms are calculated using the Coulomb law. The tensile elastic-electro coupling properties and behaviors of zigzag and armchair graphene are investigated by molecular dynamics method using the adaptive intermolecular reactive bond order (AIREBO) potential. The results show electric charges affect the Young’s modulus, the critical stress and fracture mechanism of zigzag and armchair graphene. Then the size dependent of elastic-electro coupling properties is discussed briefly.Thirdly, the elastic-electro-thermal coupling properties and behaviors of zigzag and armchair graphene at different net charges and temperatures are discussed by molecular dynamics method with AIREBO potential. The temperature is controlled by Nose-Hoover method. The tensile stress-strain curves of zigzag and armchair graphene are obtained at different temperature. The results show the Young’s modulus is decreasing with the increasing of net charges, and the critical stress is decreasing with the increasing of temperature.Finally, an analytical model based on molecular mechanics and law of conservation of energy is presented to relate the elastic properties of graphene to its atomic structure. We drive closed-form expressions for Young’s modulus of graphene as a function of bond length and bond angle. The size dependence of zigzag and armchair graphene can be discussed by the present method.In this paper a preliminary effort is presented to discuss the coupling mechanical behavior, the mechanism of graphene under the effect of mechanical load, thermal load and electric field, the chiral properties and the size-effect of graphene. Some meaningful results are obtained and are helpful for the design and application of various nanodevices based on graphene.