First-principles study on electronic structures of graphitic compounds, BC_3 and its families

点击翻译按钮获取中文摘要

The recently synthesized graphitic compounds, BC_3, C_3N and BC_2N,are new layred materials and some carbon atoms in graphite, the most typycal layred material, are substituted by boron and/or nitrogen atoms. We study theoretically electronic structures of these graphitic compounds. The band structures are determined in a local-density-functional formalism using the self-consistent numerical-basis-set LCAO method.We also estimate the amount of the charge transfers among the individual atoms.The calculated band structures of graphitic compounds show that the valence bands are constituted by sigma band and pi band. These structures can be well understood based on those of the host material, graphite, but our result for BC_3 is different from that of Tomanek et al. Their band structure has a peculiar feature of the existence of pi band above the Fermi level. This may be due to the difference of the methoud of the band structure calculation.As for the charge transfer among the individual atoms, we confirm that the amounts of the charge transfer are uniquely determined by the difference of atomic energy levels of constituent atoms which corresponds to that of electronegativities of those atoms.The calculated result indicates that boron acts as a donor and nitrogen acts as an acceptor. This result also suggests that graphitic materials have the mixed bond character of the sp^2 hybridized covalent bond typical to the honeycomb network and ionic bond.We also investigate the electronic and bond structures of fullerene families and carbon nanotubes.References include some results for these studies.