Investigation Of The Thermoelectric Properties Of Graphyne Nanotubes

Recently,the problem of energy shortage and environmental pollution is becoming more and more serious.In order to solve these two problems,thermoelectric conversion technology has attracted extensive attention.Thermoelectric materials can achieve direct conversion between electric energy and heat energy,is a new type of energy material whose conversion efficiency can be evaluated by a dimensionless quality factor ZT.Since graphene was successfully prepared from experiment in 2004,carbon nanomaterials have become a hot topic for researchers.Research shows that graphene has good electronic and mechanical properties,and can be applied to many areas of practical life.However,graphene is not an excellent thermoelectric conversion material,which is mainly due to its high thermal conductivity(at room temperature,the thermal conductivity of the monolayer graphene can reach 5.30×103W/mK In order to make up for the shortage of this nature,scientists have explored various ways to improve the thermoelectric properties of graphene and its derived structure.It is found that the thermal conductivity can be significantly reduced by the construction of different structures,doping and strain,and then the efficiency of thermoelectric conversion is improved.At the same time,scientists turned their research targets to other isomorphs of carbon.Graphyne is a new kind of carbon allotrope of materials.In this paper,based on the density functional tight binding model(DFTB),combined with the nonequilibrium Green function(NEGF),we investigated the thermoelectric transport properties of different types of graphyne and the thermoelectric performance of graphyne nanotube via applying radial strain.These studies can lay a theoretical foundation for the design and preparation of graphyne based thermoelectric devices.The main contents of this paper are as follows:1?We have studied the thermoelectric properties of four different kinds of graphyne nanotubes with similar diameter.The results show that the thermal conductivity depends mainly on the number of alkyne bonds in the structure of graphyne nanotubes,of which the thermal conductivity of alpha-GNTs is the lowest,and the thermal conductivity of gamma-GNTs is the largest.Moreover,the thermoelectric quality factors of armchair and zigzag 6,6,12-GNTs and gamma-GNTs are larger.We studied the 6,6,12-GNTS thermoelectric quality factor ZT along with the change of nanotubes diameter.The results show that the ZT of the zigzag 6,6,12-GNTs decreases gradually with the change of the diameter of the tubes.2?Taking ZGNTs as an example,we have studied the effect of radial strain on the thermoelectric properties of y-GNTs.It is found that the ZT value increases first and then decreases with the increase of strain.We also studied the thermoelectric properties of graphyne nanotubes with different sizes and chiral with strain.The results show that proper thermal strain can significantly improve the thermoelectric conversion efficiency of graphene nanotubes.