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Molybdenum disulfide (MoS 2 ) is a promising layerstructured material for use in many applications due to its tunable structural and electronic properties in terms of its structural phases. Its performance including efficiency and durability is often dependent on its mechanical properties. To understand the effects of the structural phase on its mechanical properties, a comparative study on the mechanical properties of bulk 2H, 3R, 1T, and 1T′ MoS 2 was conducted using the first-principles density functional theory. Since considerable applications of MoS 2 are developed through strain engineering, the impact of the external pressure on its mechanical properties was also considered. Our results suggest a strong relationship between the mechanical properties of MoS 2 and the structural symmetry of its crystal. Accordingly, the impacts of the external pressure on the mechanical properties of MoS 2 also greatly vary with respect to the structural phases. Among all of the considered phases, the 2H and 3R MoS 2 have a larger bulk modulus, Young's modulus, shear modulus, and microhardness due to their higher stability. Conversely, 1T and 1T′ MoS 2 are less strong. As such, 1T and 1T′ MoS 2 can be a better candidate for strain engineering.

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Transition metal dichalcogenide (TMD) monolayers attract great attention due to their specific structural, electronic and mechanical properties. The formation of their lateral heterostructures allows a new degree of flexibility in engineering electronic and optoelectronic devices.However, the mechanical properties of the lateral heterostructures are rarely investigated. In this study, a comparative investigation on the mechanical characteristics of 1H, 1T' and 1H/1T' heterostructure phases of different TMD monolayers including molybdenum disulfide (MoS2) molybdenum diselenide (MoSe2), Tungsten disulfide (WS2), and Tungsten diselenide (WSe2) was conducted by means of density functional theory (DFT) calculations. Our results indicate that the lateral heterostructures have a relatively weak mechanical strength for all the TMD monolayers. The significant correlation between the mechanical properties of the TMD monolayers and their structural phases can be used to tune their stiffness of the materials. Our findings, therefore, suggest a novel strategy to manipulate the mechanical characteristics of TMDs by engineering their structural phases for their practical applications.

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