| Over the past decade,two dimensional(2D)materials have attracted great attention due to their excellent physical properties,and are very promising in application in the future electronic devices.Due to the reduction of construction in the direction along the layer thickness,the 2D materials possess special mechanical properties which are different from bulk materials.Therefore,it is necessary to investigate the mechanical properties of 2D materials,especially their failure behavior caused by the external load,for the future application of the electronic devices.Meanwhile,the heterojunction,which consists of two or more 2D materials through the van der Waals force,also has promising applications.In this paper,2D black phosphorus,tin selenide and heterojunction of black phosphorus and tin selenium were systematically studied.The first-principles method was introduced to investigated the elastic modulus,the tensile strength,the structural change and the Poisson’s ratio of black phosphorus and related structures under tensile strain.The stress-strain curves of different structures and the structure changes during the stretching process were obtained from first-principles calculations.The mechanical properties and failure behavior of black phosphorus and related structures under external load were analyzed and discussed.Some main conclusions are summarized as following:1.For the black phosphorus and related structures,the layer thickness has impact on its tensile strength,fracture strain and elastic constant.The smaller the number of layers,the greater the tensile strength and the elastic constant the materials have.Black phosphorus and tin selenide show strong anisotropy: the elastic constant and tensile strength along zigzag direction is significantly higher than that along the armchair direction.2.Single layer black phosphorus shows the negative Poisson’s ratio phenomenon,but it disappears in the multi-layer black phosphorus.Unlike the black phosphorus,our calculations show that both monolayer and double-layer of tin selenide show negative Poisson’s ratio properties.3.The heterojunction consisting of black phosphorus and tin selenide layers shows interesting isotropic properties.This is different from black phosphorus and tin selenide which show strong anisotropy.For heterojunction,the mechanical properties are similar to the two-layer tin selenide along the zigzag direction,but the tensile strength is improved by about 25%.While along the armchair direction,the mechanical properties are similar to the two-layer black phosphorus,and the tensile strength is reduced by about 18%,but it is still 110% stronger than that of two-layer tin selenite in this direction. |
