Thomas Siby, Ajith K M, Lee Sang Uck, Valsakumar M C
Department of Bionano Technology, Hanyang University Ansan 15588 Korea
Department of Physics, National Institute of Technology Karnataka (NITK) PO: Srinivasnagar Mangalore India - 575025.
RSC Adv. 2018 Jul 31;8(48):27283-27292. doi: 10.1039/c8ra02967a. eCollection 2018 Jul 30.
Molecular statics and dynamics simulations were performed to investigate the mechanical properties of a monolayer graphene sheet using an efficient energy method and strain-fluctuation method. Using the energy method, we observed that the mechanical properties of an infinite graphene sheet are isotropic, whereas for a finite sheet, they are anisotropic. This work is the first to report the temperature-dependent elastic constants of graphene between 100 and 1000 K using the strain-fluctuation method. We found that the out-of-plane thermal excursions in a graphene membrane lead to strong anharmonic behavior, which allows large deviations from isotropic elasticity. The computed Young's modulus and Poisson's ratio of a sheet with an infinite spatial extent are 0.939 TPa and 0.223, respectively. We also found that graphene sheets with both finite and infinite spatial extent satisfy the Born elastic stability conditions. We extracted the variation in bending modulus with the system size at zero kelvin (0.83 eV) using a formula derived from the Foppl-von Karman approach. When the temperature increases, the Young's modulus of the sample decreases, which effectively reduces the longitudinal and shear wave velocities.
采用高效能量法和应变涨落法进行分子静力学和动力学模拟，以研究单层石墨烯片的力学性能。使用能量法，我们观察到无限大石墨烯片的力学性能是各向同性的，而对于有限尺寸的片材，其力学性能是各向异性的。这项工作首次使用应变涨落法报道了100至1000 K之间石墨烯的温度依赖性弹性常数。我们发现，石墨烯膜中的面外热偏移会导致强烈的非谐行为，这使得其与各向同性弹性有很大偏差。计算得到的具有无限空间范围的片材的杨氏模量和泊松比分别为0.939 TPa和0.223。我们还发现，具有有限和无限空间范围的石墨烯片均满足玻恩弹性稳定性条件。我们使用从Foppl-von Karman方法推导的公式，提取了零开尔文（0.83 eV）时弯曲模量随系统尺寸的变化。当温度升高时，样品的杨氏模量降低，这有效地降低了纵向和剪切波速度。
