Study On The Electronic Properties Of M₆X₆(M=Mo,W;X=S,Se,Te) Nanowires And Arrays

With the rapid development of computational science,theoretical simulation plays a key role in condensed matter physics.It can not only explain novel physical phenomena from the atomic size level,but also predict the physical and chemical properties of new materials,providing theoretical guidance for experimental research.Transition metal chalcogenide nanowires have excellent physical and chemical properties,such as high elasticity and mechanical stability,which have aroused wide interest among researchers.Recently,Mo₆Te₆nanowires with a certain array arrangement were successfully prepared experimentally through vacuum annealing of multilayer 2H-Mo₆Te₆.The electronic properties of this array structure have changed compared to a single Mo₆Te₆ nanowire.Unlike other nanomaterials,we still know very little about the M₆X₆ nanowire array,and its structural stability and electronic properties are still unclear.In addition,M₆X₆ nanowires are considered as potential"connecting wires"for micro-nano devices due to its high mechanical stability.Also,understanding the performance of nanowires under bending conditions is of great significance to the practical application.Therefore,it is very important to theoretically explore the effect of its nanowire array and bending.The first part mainly explores the stability and electronic properties of M₆X₆(M=Mo,W;X=S,Se,Te)nanowire arrays;the second part examines the stability and electronic properties of the Mo₆S₆ and Mo₆Te₆ nanowires under bending conditions.(1)The stability and electronic properties of M₆X₆(M=Mo,W;X=S,Se,Te)nanowire arrays.Through the first-principles method,we systematically investigated the mechanical stability of nanowires in square arrays,centered square arrays,hexagonal I and hexagonal II arrays.We found that the hexagon I array structure is the most stable.At the same time,it is found that the bandgap of the M₆X₆(M=Mo,W;X=S,Se)nanowire array does not change compared to a single nanowire;the M₆X₆(M=Mo,W;X=Te)nanowire array has changed from the semiconducting properties of a single nanowire to a metallic property due to the coupling between the nanowires.This shows that M₆X₆nanowires are potential good materials for micro-nano devices,and can be used to make electromechanical switches that transmit information.(2)Stability and electronic properties of bended M₆X₆(M=Mo;X=S,Te)nanowires.We studied the stability and electronic properties of nanowires under different bended degrees by using first-principles methods.It was found that Mo₆S₆ and Mo₆Te₆ nanowires have different mechanical properties under different radii of curvature.For example,it can be restored to a linear shape under small bends,showing that it has a certain degree of toughness.As the bend increases,the degree of bending of the nanowire will decrease after relaxed.And the further increase the bend,the nanowire will break.Interestingly,the calculation results show that different structures have different responses to curvature:the electronic properties of Mo₆S₆nanowires do not change with curvature,remaining the original metal characteristics,while Mo₆Te₆ nanowires gradually change from semiconductor to metal as the curvature increases.This shows the potential application value of Mo₆S₆ and Mo₆Te₆ nanowire materials in flexible micro-nano devices.