Mechanical Fracture of Bilayer MoS₂ with Grain Boundaries

Grain boundaries (GBs) are inevitably formed in bilayer MoS2 during the synthesis process, which could influence the mechanical and electronic properties of the material. Because of their significance in electronic applications, an in-depth understanding of GBs in bilayer MoS2 is crucial to avoid mechanical failures. We have extensively investigated the mechanical behaviors and fracture of bilayer MoS2 with different GBs based on the first-principles calculations. Bilayer MoS2 with GBs energetically prefers to form the 2H stacking pattern, and the presence of GBs weakens the mechanical properties of bilayer MoS2, which is associated with the tensile orientations and GBs structures. The mechanical properties of bilayer MoS2 with GBs are anisotropic, and the zigzag direction exhibits better strength than the armchair direction. The GB containing four-membered ring is easier to break, while the GB containing 8-membered ring exhibits a stronger fracture resistance to external stretching. Our results have shown that bilayer MoS2 has better resistance to GBs than monolayer MoS2, which provides it broader applications for next-generation electronic devices.