Molecular Dynamics Study Of The Tensile Mechanical Properties Of Single Crystal Copper Nanowires

With the development of micro/nano electromechanical system(MEMS/NEMS), the researches on the mechanical properties of nanowires as the basic element of micro/nano electromechanical devices have received extensive attentions. Using the molecular dynamics simulation method is an important way to study the mechanical properties of nanopore defect nanowires, but the results of the present study still have a series of existence questions, such as inadequately considering the original nanopore defect structure parameters、external factors(i.e., temperature and strain rate) and mechanical properties index,especially inadequately researching nanopores designed into nanowires as a benifical factors. Therefore, this thesis uses molecular dynamics simulation method to research the tensile mechanical properties of single crystal copper nanowires with original nanopore defects at strain rates and temperatures. Organization of the content is as follows:First of all, the influences of temperatures and strain rates on the tensile mechanical properties of perfect nanowires of single crystal copper are studied. A molecular dynamic simulation environments are constructed. On the basis of the basic instructions of LAMMPS, the execute code of the 3D geometry models of the ideal single crystal copper nanowires, relaxation and tension deformation process are compiled. Based on reasonably determinating simulation parameters, molecular dynamics simulation experiments are carried out, It is observed that the curve characterized as linear function between the first peak point and the first lower yield point on the stress strain curve shows a linear relationship which is different from elastic state, it is concluded from the stress strain rule of this elastic plastic mixing stage; the effect of two external factors(i.e., strain rate and temperature) on mechanical properties of single crystal copper perfect nanowires are analyzed.Secondly, the influence of the original nanopore defect structure parameters on the mechanical properties of single crystal copper nanowires at strain rates and temperatures are systematically studied. Molecular dynamics simulation 3D models for the single crystal copper nanowires with nanopore defects containing three original nanopore defect structure parameters(i.e., nanopore defect structure types and nanopore defect structure locations and model structure types) are established, two external factors(i.e., temperature and strain rate) are considered. Based on reasonably determinating simulation parameters, molecular dynamics simulation experiments are carried out. Finally the influence of the original nanopore defect structure parameters on the mechanical properties of single crystal copper nanowires at strain rates and temperatures are studied.Finally, in the case of the optimal conditions of mechanical properties of nanowires, the determination of nanopore structure parameters and external conditions is studied. Molecular dynamics simulation 3D models for the single crystal copper nanowires with nanopore containing three original nanopore structure parameters(i.e., nanopore structure types and nanopore structure locations and model structure types) are established, two external factors(i.e., temperature and strain rate) are considered,, the interaction between the elements and no interaction between elements are considered by using the mixed orthogonal experimental method, the corresponding internal structure(i.e., nanopore structure types and nanopore structure locations and model structure types) and external conditions(i.e. temperature and strain rate) are calculated under the optimum mechanical properties, the optimal conditions of the specific mechanical performance is determined.In this thesis, it could be found that the relation between the plastic modulus and strain rate shows a logarithmic function, and it showed a quadratic function relation with temperatures; The corresponding optimal setting values for the maximum nanowire plastic modulus are the strain rate of 2.5×108s-1, temperature of 0.1k, spheroidal nanopore structure types, cylinderical models surface strucutues, and the nanopore strucutue position on the model surfaces. The research results of this thesis provide a basic theoretical guidance for understanding of the mechanical properties of nanopore defect nanowires.