| It is well known that nitrogen and boron atoms are typical substitutional dopantsin carbon materials. They can inject electrons and holes, thus changing their electronicand transport properties. Although the fixed sizes graphene had been researched, thestudy of different sizes doped graphene is still vacant.In this work we focus on graphene molecules with hybrid atoms of boron ornitrogen. All the structures are optimized by the B3LYP/6-31G(d, p) method.(N1=3，N2=3thirteen benzenes；N1=4，N2=3eighteen benzenes；N1=6，N2=3twenty-eightbenzenes；N1=7，N2=3thirty-three benzenes)It is found that the bond length of graphene will be affected by doped boron andnitrogen atoms. For nitrogen-doped graphene, the value of carbon-hydrogen bond andcarbon-nitrogen bond are smaller than pure graphene at the corresponding positions.For boron-doped graphene, the value of carbon-hydrogen bond and carbon-nitrogenbond are bigger than pure graphene at the corresponding positions.The electronic structures of the doped graphene nanoribbon are different fromthose of pure graphene nanoribbon by comparing the HOMO,LUMO and their energygap of pure graphene and doped graphenes. The energy gap of one boron dopedgraphene or one nitrogen doped graphene is bigger than pure graphene, so that thedoped graphene transmit from the conductor nature to the semiconductor nature.In order to analyze those electronic structures distinctly, we protract the DOS ofdoping graphenes. As the Fermi level of the doped graphene locate at zero area of theDOS, the conductivity of one boron and one nitrogen doped graphene are smaller thanpure graphene.The ABEEMσπ parameters of doping graphene were determined based on thecharge distribution calculated by the HF/STO-3G method. According to ourcalculation, the charge distributions of doping graphene from the ABEEMσπ modelare consistent well with the results from the ab initio calculations. It can be seen thatour model can be used for larger molecular systems mentioned above. |
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