Finite temperature mechanics of multilayer 2D materials

Y Chen and WG Ouyang and K Zhou and HS Qin and YL Liu, EXTREME MECHANICS LETTERS, 52, 101612 (2022).

DOI: 10.1016/j.eml.2022.101612

Thermal fluctuation at finite temperature is a common feature for bio- membranes and two-dimensional (2D) layered crystals due to their flexibility of bending deformation. Previous works regarding thermal fluctuations of 2D materials mainly focused on monolayer systems, the finite temperature mechanics of multilayer 2D materials was rarely explored, especially the effect interlayer shear on the thermal fluctuation of multilayer 2D materials. In this work, we introduced a multi-beam shear model based on the statistical mechanical description of multilayer graphene (MLG) to explore the effects of thermal fluctuations. Various factors are considered, such as temperature T, size L, layer number n, interlayer shear modulus G and biaxial pre- strain epsilon(0) etc. Within the harmonic approximation, the average root-mean-square height due to thermal fluctuation is found to be scaled as h proportional to root ln L, which is distinctly different from that of monolayer graphene with a linear scaling (h proportional to L) within the harmonic approximation. In addition, h decreases with the increase of layer number n and interlayer shear modulus G. Overall, the thermal fluctuation of MLG is bounded by two theoretical limits, i.e., the case of perfect bonding without interlayer sliding and smooth interlayer sliding without interlayer shear stress. Furthermore, the thermal fluctuations also reduce the tangent biaxial Young's modulus of multilayer 2D materials. The systematical MD simulations for MLG are performed and validate the effectiveness of the harmonic analysis. (c) 2022 Elsevier Ltd. All rights reserved.

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