Thermal Properties Of Two Types Of 2D Carbon Allotropes

Owing to the versatile flexibility of carbon in forming three different hybridization states(sp,sp~2,sp~3),various carbon allotropes can be produced such as fullerene,carbon nanotube and graphene,etc.With the development of scientific research,more and more carbon allotropes have been discovered and studied.Studies have shown that low dimensional carbon materials,such as carbon nanotube,graphene and graphyne show excellent properties in thermal transport.Inspired by line defects in graphene,two types of new 2D carbon allotropes comprised of octagons and pentagons were proposed.The studies based on first-principle calculations shown that the two structures are kinetic stability and exhibit electronic anisotropy,which have interesting potential applications in electronic devices.Considering the high thermal conductivities of low dimensional carbon materials,we are also interested in the thermal properties of these two materials.And to solve the heat dissipation of these two materials in electronic devices in future,we study the thermal properties of them by molecular dynamics simulation.The main results are as follows:(1)The non-equilibrium method was used to study the effect of model length on thermal conductivity by establishing model with the same width but different length.The thermal conductivity of these two materials in macroscopic sizes has been obtained by an inverse fitting procedure and combining the results of equilibrium method.(2)The results obtained by studying the thermal conductivity of model in two chiral directions shown that the thermal properties of the two materials are nearly isotropic.(3)Based on the classical lattice thermal transport equation,three essential thermal parameters of the two materials,heat capacity,phonon mean free path and phonon group velocity were calculated.The thermal properties of these two materials were further studied based on the comparison with graphene.(4)The effects of temperature and uniaxial tensile strain on thermal conductivity of these two materials were studied.Thermal conductivity was found to decrease with the increasing temperature in the range of 200 K to 500 K,which can be attributed to phonon scattering due to increasing temperature.Thermal conductivity was further found to decrease with the increasing tensile strain,which can be attributed to phonon softening.Our studies on the influence of temperature and strain on thermal conductivity of the two materials provide a theoretical basis for its application in thermal management and electronic devices.