Molecular dynamics study on the uniaxial tensile behavior of mono-layer MoTe2 film defected by mirror twin boundary

YF Shao and R Cao and YL Liu, COMPUTATIONAL MATERIALS SCIENCE, 230, 112481 (2023).

DOI: 10.1016/j.commatsci.2023.112481

High-density mirror twin boundaries, which exhibit fascinating electronic properties, are revealed in low-dimensional MoTe2 films in recent years. Mechanical behavior plays a key role in the application of MoTe2 with these novel defects. In this paper, a mono-layer MoTe2 crystal was constructed, and the 4|4P mirror twin boundary, which is the most easily observed in the experiment, was embedded in the center of model. The molecular dynamics method combined with Stillinger-Weber potential function was used to simulate the uniaxial tension, the effects of this defect on the fracture stress of monolayer MoTe2 were studied. Results show that the 4| 4P mirror twin boundary has little effect on the Young's modulus of MoTe2, but reduces the fracture stress. Larger size of the mirror twin boundary, lower temperature and the armchair loading direction can make the decrease of fracture stress more significant, however the size effect is much weaker when the film is stretched along the zigzag direction. Turning the MoTe2 model with a specified large mirror twin boundary into ternary MoTe2(1-x)Se2x model by replacing some Te atoms with Se impurities randomly and uniformly, then setting the condition of temperature and Se concentration into 12 groups for each loading direction, the ratio of the fracture stress derived from the defected model to the value obtained from ideal model almost remains unchanged. Finally, this phenomena are analyzed based on brittle fracture theory.

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