Mechanical Properties Of Single-Layer Molybdenum Disulfide Based On The Computational Methods At Molecular Scale

As a novel nanoscale two-dimensional material,the single-layer molybdenum disulfide?SLMoS₂?has a wide potential application in micro-and nano-scale electronic components because of its special band structure and semiconductor property.In general,the structural design of electronic components is the crucial factor affecting the function and service life in practical application,whose rationality and reliability are often relied on the accurate understanding on the mechanical property of materials.Therefore,the research on the mechanical property of SLMoS₂ is of great scientific significance and actual application to the design and fabrication of the micro-and nano-scale electronic components.Based on the computational method at molecular scale,we investigate the mechanical properties of SLMoS₂ with finite size under tensile and shear forces,respectively,and the corresponding variations with the characteristic sizes.Firstly,the mechanical behavior of SLMoS₂ under uniaxial tension is described analytically based on the molecular mechanics method.By constructing the corresponding molecular mechanics model,the analytical expression of the elastic modulus and Poisson's ratio with the change of the characteristic size is obtained.Meanwhile,the numerical simulations of uniaxial tension deformations along the armchair and zigzag directions based on the molecular dynamics method are carried out,respectively,which verify the rationality and correctness of the constructed theoretical models.The computational results indicate that the mechanical properties?the elastic modulus and Poisson's ratio?of SLMoS₂ exhibit an obvious anisotropy when the characteristic size of SLMoS₂ is small;the increase of the characteristic size along the armchair and zigzag directions can effectively enhance the elastic modulus along the corresponding directions,but weaken them along the other directions,respectively;the Poisson's ratio decreases with the increase of the characteristic sizes,but almost remains unchanged when only the characteristic size along the armchair direction changes;when the sizes along the two directions changes simultaneously,the characteristic size along the armchair direction plays a dominant role in the variation of the elastic modulus,and the characteristic size along the zigzag direction plays a dominant role in the variation of the Poisson's ratio.Secondly,the mechanical behavior of SLMoS₂ under pure shear load is described analytically based on the molecular mechanics method.By constructing the corresponding molecular mechanics model,the analytical expression of the shear modulus with the change of the characteristic size is obtained.Meanwhile,the numerical simulations of pure shear based on the molecular dynamics method are conducted,which further verifies the rationality and correctness of the constructed theoretical models.The computational results indicate that when the characteristic size along the zigzag direction is fixed,the shear modulus increases with the increase of the characteristic size along the armchair direction;when the characteristic size along the armchair direction is fixed,the change of the characteristic size along the zigzag direction has almost no effect on the shear modulus,and the shear modulus always keep constant,which demonstrates the shear modulus has a unidirectional size dependence only relating to the characteristic size along the armchair direction.As the further increase of characteristic size,the elastic modulus and Poisson's ratio of SLMoS₂ along the armchair and zigzag directions tend to be consistent,respectively.When the characteristic size tends to infinity,the elastic modulus,Poisson's ratio and shear modulus all approach to the saturated values,namely,179.10 GPa,0.22 and 73.43 GPa respectively.The change trend of mechanical properties indicates that the SLMoS₂ gradually transits from anisotropic material to isotropic material with the increase of characteristic size.The research results in this dissertation provide important theoretical references for the design and application of molybdenum disulfide-based micro-and nano-scale electronic components.