Structural Phase Transformation in Strained Monolayer MoWSe₂ Alloy

Molecular dynamics (MD) simulations are performed to examine atomistic mechanisms of defect formation and crack propagation in a strained monolayer MoWSe₂ alloy. The system consists of a 1.0 m x 1.0 m MoSe₂ monolayer with a pre-crack and random patches of WSe₂. Under strain, the crack meanders as it propagates through the system and branches into two daughter cracks when it crosses the MoSe₂/WSe₂ interface and enters the WSe₂ patches. The most dramatic change occurs in the process zone around the crack tip, where large stress concentration and the resulting biaxial tensile strain trigger an irreversible local structural phase transformation from the ground state 2H crystal structure to the 1T crystal structure. This is consistent with experimental observations in an MoWSe₂ alloy.