Thermal Conductivity Of Graphyne Nanotubes:Amolecular Dynamics Simulations

As one of non-natural allotrope of carbon, graphyne nanotubes exhibit specialmechanical properties and electronic structure. Graphyne nanotubes aresemiconductors with the direct band gap in the range of0.40eV~1.3eV and Young’smodulus between0.44and0.50Tpa. These intriguing characters indicate the potentialapplications of graphyne nanotubes in the field of electronic devices and energystorage. Simultaneously, the investigation of thermal properties of graphynenanotubes is very necessary, but it has not been well studied.In this paper, the nonequlibrium molecular dynamics simulation is used toinvestigate the thermal conductivity of graphyne nanotubes. The results are dividedinto some sections as follows：1. Nonequlibrium molecular dynamics method is adopted to study the size effecton the thermal conductivity of graphyne nanotubes. The results demonstrate that thethermal conductivity of graphyne nanotubes enhances with the increasing of lengthand follows the power law of k~L. Compared with carbon nanotubes and graphenenanoribbons, graphyne nanotubes have lower value of, which indicates that thelength dependence of thermal conductivity in graphyne nanotubes is weaker than thatin carbon nanotubes and graphene nanoribbons; We also find that the thermalconductivity of graphyne nanotubes weakly increases with the increasing of diameter.The thermal conductivity of the armchair graphyne nanotubes is higher than that ofthe zigzag ones in the case of same size, which demonstrates that thermal conductivityof graphyne nanotubes is anisotropic.2. The phonon density of states (DOS) is used to explain the mechanism of thedifference of thermal conductivity between graphyne nanotubes, graphenenanoribbons and carbon nanotubes. The carbon atoms on the acetylenic linkage havea lower thermal efficiency than those on the benzene. The matching degree of DOS ofatoms on the acetylenic linkage and atoms on the benzene is poor, which suppressesthe thermal conductivity of graphyne nanotubes.3. We simulate the thermal conductivity of graphyne nanotubes with differenttemperature. The results show that the thermal conductivity of graphyne nanotubesdecreases with the increasing of temperature, but above1000K, the temperatureeffect is very weak.4. It is found that both tensile and compressive axial strain result in the reduction of thermal conductivity of graphyne nanotubes.5. We also simulate the influence of vacancy defects at different positions(beneze and acetylenic linkage) on the thermal conductivity of graphyne nanotubes.The vacancy defects significantly reduce the thermal conductivity of graphynenanotubes.