Linear and nonlinear buckling analysis of double-layer molybdenum disulfide by finite elements

This study aims to examine the buckling stability behavior of pristine and defected double-layer molybdenum disulfide (DLMoS2) through a finite element modeling approach. Finite element models of DLMoS2 cantilever sheets are developed by establishing relationships between the molecular dynamics force field and structural mechanics to calculate the equivalent physical properties of in-plane Mo-S covalent bonds and inter-plane van der Waals (vdW) interactions. The proposed finite element method is used to conduct both linear eigenvalue-based and nonlinear modified Riks buckling analysis to predict the critical buckling stress, the first four in-phase and anti-phase buckling mode shapes, and the buckling deflection magnitudes of DLMoS2. The impact of atomic configuration on the buckling stability of DLMoS2 is investigated by studying nanosheets with armchair and zigzag chirality coupled with AA3 and AB1 stacking modes. The influence of defects on the buckling behavior of MoS2 is studied by considering nanosheets with 2%, 6%, and 10% sulfur and molybdenum vacancy defects. The results revealed that nonlinear analysis is necessary to obtain reliable predictions of the buckling behavior of DLMoS2. MoS2 nanosheets with AB1 stacking mode and zigzag chirality demonstrate a more stable buckling behavior and higher post-buckling deflection magnitude compared to nanosheets with AA3 stacking mode and armchair chirality. Although both defect types reduce the buckling stress, the results show that sulfur vacancies reduce buckling load more severely than molybdenum vacancies. Furthermore, the results show that sheets with sulfur vacancies display more complex buckling mode shapes than sheets with molybdenum va-cancies. The critical buckling stress decreased as the defect density increased, regardless of the mode shape and defect type.