Molecular Dynamics Study Of Thermal Conductivity For Graphyne Nanoribbons

Graphyne is one kind of two-dimensional structure materials which is hybridized by sp and sp2.It contains rich chemical bonds between carbon atoms.With the development of graphyne technology,more and more attention has been paid to its performance,and its thermophysical property is one of the most important properties.It's difficult to measure the thermophysical property of graphyne due to its special structure,and the experimental measurement method couldn't reflect the microscale thermal conduction mechanism.However,it can be well simulated by molecular dynamics method.Presently,the research on graphyne is mainly focused on optics,electricity and some other aspects,and relatively few reports on its thermal properties.Therefore,in order to study the thermal conductivity of graphyne nanoribbons from the micro scale,the non-equilibrium molecular dynamics method has been used.Firstly,the relationship between the thermal conductivity and the length,width,edge type,potential function and temperature of graphyne nanoribbons has been simulated.It is found that the thermal conductivity of graphyne nanoribbons increases with the increase of the length and width of the nanobelts.This is mainly because the propagation of phonons in the surface suffered less hindrance with the increase of the cross sectional area,and the scattering of the edge phonons is relatively weaken.The thermal conductivity of the armchair and zigzag graphyne nanoribbons that similar in size,its changing rate with the increase of the length and width is different,which verified that the graphyne nanoribbons have anisotropy.This is mainly due to the different propagation velocity of phonons in different directions and the scattering of phonons by different boundary structures is not the same.The thermal conductivity of graphene nanoribbons is higher than that of graphyne nanoribbons,which is mainly related to the special structure of graphyne.Secondly,the effect of vacancy defects on the thermal conductivity of graphyne nanoribbons has been simulated in this paper.It is inevitable that vacancy defects exist in the lattice structure during the preparation of' graphyne nanoribbons,which will anffect its physical properties.It is found that the vacancy defects lead to the decrease of the thermal conductivity of graphyne nanoribbons,and the more the number of vacancy defects,the lower the thermal conductivity.The contribution of the carbon atoms on acetylene chain on the thermal conductivity of graphene nanoribbons is less than that of the carbon atoms on the benzene ring.This is mainly because the vacancy defect affects the mean free path of the phonon,which affects the thermal conductivity of graphyne nanoribbons.Finally,the effect of field force on the thermal conductivity of graphyne nanoribbons has been simulated.It is found that the thermal conductivity of graphyne nanoribbons decreases first and then increases with the increase of the applied field force which is in the same direction with the heat flux,and is gradually increased with the increase of the applied field force which is in the vertical direction with the heat flux.With the increase of the frequency of the applied field force,the thermal conductivity of graphyne nanoribbons tends to decrease.