Study On Microscale Effects On Mechanical Rigidity Of Single Walled Carbon Nanotubes Using Molecular Mechanics

Since the discovery of carbon nanotubes in the 1990 s,it has attracted widespread attention.The excellent mechanical properties of carbon nanotubes have great potential in the application of nanoresonators.However,as a discrete atomic system,its microscopic discontinuous essence makes its mechanical properties have a scale effect that cannot be ignored,namely the microscale effect.For carbon nanotube resonators,the frequency is up to GHz,and slight changes in rigidity will have a significant impact on frequency.Previous theoretical studies on the relationship between tube length and rigidity are controversial.The corresponding experimental research is difficult and costly.Therefore,it is important to study the microscale effect of carbon nanotube rigidity.The micro-scale effects of carbon nanotube rigidity of previous studies are mainly based on numerical simulation of atomic empirical potential and continuous simulation based on continuum theory.The accuracy of the former simulation depends on the empirical potential,the latter lacks a solid micro-theoretical basis and requires other reliable methods to verify its rationality.In order to further explore this problem,based on the molecular mechanics method,using high-quality atomic empirical potential,combined with continuous theory,the micro-scale effect of singlewalled carbon nanotube stiffness is deeply studied.The main work content is:First,the optimized Tersoff potential is used to characterize the tensile rigidity of singlewalled carbon nanotubes with different chirality,diameter and length.The results show that the micro-scale effect reduces the tensile rigidity of single-walled carbon nanotubes,and the tensile rigidity increases with length and gradually converges.The non-local one-dimensional rod model is compared with the results of molecular mechanics,and the non-local parameters reflecting the micro-scale effect are extracted.It is found that the non-local parameters reflecting the micro-scale effect increase with the increase of diameter,which confirms the result of molecular mechanics simulation based on the early atomic empirical potential.The bending rigidity of single-walled carbon nanotubes was further characterized by a similar method.The results show that the bending rigidity of single-walled carbon nanotubes increases with the length and convergence under different mechanical boundary conditions.The non-local parameters of single-walled carbon nanotubes under bending behavior increase with diameter,thus solving the controversy of the previous studies on this issue in non-local continuous simulation..