Molecular dynamics simulations for tensile behaviors of mono-layer MoS2 with twin boundary

YF Shao and FS Meng and JH Li and X Zhao, ACTA PHYSICA SINICA, 68, 216201 (2019).

DOI: 10.7498/aps.68.20182125

Grain boundary (GB) plays a key role in determining the electrical and mechanical properties of monolayer transition metal dichalcogenide (TMDC), however it is still a challenge to uncover the GB-mediated TMDC material experimentally. In this paper, the effect of twin boundary on the tensile behaviors of monolayer MoS2 is investigated by using the molecular dynamics simulation combined with the Stillinger-Weber potential. Mono-layer MoS2 model under the varied size and temperature condition is adopted. Stress calculation is performed by using Virial theorem. The results are obtained as follows. 1) Twin boundary promotes the brittle fracture of an undefected mono-layer MoS2 sheet by inducing the nucleation of the crack near boundaries, thus the fracture strength and strain are weakened. 2) Increasing the ambient temperature from 1 K to 600 K, the crack nucleation process near the twin boundary is intensely accelerated, and the fracture strength and strain are further declined. 3) Twin lamellar spacing also plays an important role in the tensile process of mono-layer MoS2, and the specimen with dense twin boundary, especially with void, shows higher fracture strain. 4) Stress analysis at an atomic level outlines the stress concentration caused by voids and the shielding effect of twin boundary. Because of the interactions between voids and twin boundary, the fracture strength and strain of a voided mono-layer MoS2 sheet can be greatly improved.

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