Theoretical Studies On The Structures And Properties Of Fullerenes With Nitrogen Dopant

Nitrogen-doped fullerenes formed by doping nitrogen atoms or related nitrides onto or inside the fullerene cages have not only the physical and chemical properties of fullerenes,but also unique properties due to the change of electronic structure caused by the incorporation of nitrogen atoms,including stability,magnetism,reactivity and so on.Theoretical calculation is an effective method to evaluate the structural stability and reactivity of nitrogen-doped fullerenes,predict physical and chemical properties and potential applications.In this dissertation,a series of nitrogen-doped fullerenes were calculated by using density functional theory（DFT）.The electronic structures,bonding patterns,catalytic reaction activity and aromaticity are analyzed,and their potential applications were predicted.First,we studied the two types of metal carbonitride clusterfullerenes by DFT calculations:cyanide(MCN@C_2n,M=metal)and carbonitride(M₃CN@C_2n)and the corresponding structures upon C（?）N interchange.The results show that the exchange of carbon atom and nitrogen atom leads to different bonding pattern of multicenter bonds for M₃CN@C_2n.Moreover,we find that the relative stability of two isomers with different positions of carbon and nitrogen atoms can be explained by hyperconjugation.In addition,the topological analysis shows that there is a weak covalent interaction between the metal and carbon cage,and obvious ionicity dominates the N/C-carbon cage interaction.Second,we studied the chemical properties of a series of azafullerenes covering different sizes and types by means of DFT calculations.Through theoretical calculations,we had studied the application of several azafullerenes in hydrogen evolution reactions.The results show that azafullerenes have good HER catalytic performance.Compared with pure fullerenes,the incorporation of nitrogen atom improves the HER activity.Through the analysis of the electron density difference,we observe that there is an obvious electron transfer between the adsorbed hydrogen atom and the carbon adsorption site,which thus promotes the activity for HER.Finally,we found that there is a certain linear relationship between the relative stability of the structure and local aromaticity by studying the structure of B₃₀N₃₀ fullerene.Therefore,we are curious about the potential role of local aromaticity in the activity for B₃₀N₃₀fullerene adsorpting small molecules.Further research found that surface sites with less negative（or more positive）NICS values can be considered as the most promising sites for adsorption of small molecules.By trying different structures,we found that the conclusion is not limited to the B₃₀N₃₀ fullerene,but also can be applied to various material surfaces with planar（such as graphenes）,curved（such as fullerenes,nanotubes）and even buckled（such as silicenes）structures,thus greatly broadening the conventional aromaticity concept.