Study On Optical Properties Of Graphdiyne

Carbon consists a rich carbon family in its unique sp,sp2,sp3 hybridization mode and variable bonding formations.In recent years,the focus of scientific research has been on low-dimensional carbon nanomaterials.After the discovery of graphene,a new two-dimensional planar structure of lower dimensional carbon nanomaterial was found by the scientists of China in 2010,which is called graphdiyne.Both sp2 and sp hybrids exist in this kind of nanostructure,so that graphene not only possesses excellent properties similar to graphene,but also has the property of semiconductors that graphene does not possess.In this paper,the properties of the material are calculated by the method of plane wave pseudopotential of the first principle by using the CASTEP module in MS?Materials studio?.By building a three-dimensional graphdiyne model,the band structure,density of states,and optical properties of it with different types and stacking modes were studied.Graphdiyne has the characteristics of three-dimensional porous and monolayered planar two-dimensional network materials.Therefore,graphdiyne has more advantages in electronic properties than graphene.Graphyne has a direct band-gap energy,and the graphdiyne band-gap energy is zero,so graphdiyne is more suitable for optoelectronic devices than graphene.The research is mainly composed of the following parts:1.By changing the number of alkyne bonds in single layer graphdiyne,the structure of single layer graphdiyne is changed,graphynes to graphdiyne of four alkynes,the four two-dimensional planar materials of graphdiyne are all direct band gap semiconductors,and the band gap decreases gradually with the increase of the number of alkyne bonds in the structure.Under the condition of parallel polarization,that is,the polarization direction of parallel incident light,the absorption spectra of four different structures of graphdiyne can reach the ultraviolet region from the infrared region.Under the non-polarized conditions,the corresponding wavelength of reflectance peak shifts gradually with the increasing number of alkyne bonds.2.By changing the stacking mode of double layer graphynes,the band gap of graphynes can be changed,and its properties are changed between metal and semiconductor.The conduction band and valence band of double layer graphynes crystal structure with the AA stacking mode overlap each other,showing the metal properties.The AB₂ and AB₃ stacking mode shows the semiconductor properties because of the existence of the direct band gap,while the AB₁ stacking mode is semiconductor with indirect band gap.3.The optoelectronic properties of the graphdiyne were changed by doping the graphdiyne with an impurity factor,and then compared with the undoped graphdiyne.Besides,the numerical simulation of the model was carried out by the density functional theory?DFT?so as to the structure and optical properties of graphdiyne and doped graphdiyne with different types were stuied.4.The molecular dynamics method is used to simulate hydrogen adsorption capacity of graphdiyne with hydrogen atom concentration.It is found that the adsorption capacity of graphdiyne increases with the hydrogen concentration,which is almost linear.However,due to the resistance of graphdiyne to hydrogenation,at room temperature and atmospheric pressure,when the concentration of hydrogen atoms is continuously increased until reaching the limit concentration of gaseousness,the adsorption rate of hydrogen atom has a maximum value.