摘要
采用DFT/BLYP方法对NbC(001)和(111)面的电子结构进行研究。计算结果表明,对于NbC(001)表面,其表面态主要集中于费米能级(EF)下方约4.5eV附近区域,并以表面Nb原子和C原子为主要成分。O2分子在该表面吸附时,趋向于吸附在表面Nb原子上。对于NbC(111)表面,其表面态集中在EF下方0.02.0eV区域,靠近EF的态具有较高的表面活性,其主要成分为表面Nb原子的4dxz/dyz成分。上述结论与光电子能谱实验结果基本一致;但由于金属原子d电子数的差异导致NbC(111)表面态成分与类似的TiC化合物并不相同。
The electronic structures of the NbC bulk, (001) and (111) surfaces have been investigated by the DFT/BLYP method. The results show that, for the NbC(001) surface, the surface state is mainly located about 4.5eV below the Fermi level(E-F), which is derived from the surface of Nb 4d and C 2p characters. When the oxygens are adsorbed on NbC(001) surface, the oxygen atoms prefer to attach on the surface of Nb atoms. For the NbC(111) surface, the surface states are centered in the range of 0.0 similar to2.0eV below E-F. The state located just below E-F consists mainly of 4d(xa)/d(yz) orbits of Nb surface and it can be ascribed to an 'active' surface state. However, since the Nb atom has more d electrons, the component of this 'active' surface state differs from that of TiC(111) surface. Our results calculated are in agreement with the experimental photoemission spectra.
基金
自然科学基金(29973006)
福州大学科技发展基金(XKJ-0105)资助项目
关键词
NBC
电子结构
过渡金属碳化物
密度泛函理论
能带结构
态密度
光电子能谱
表面态
碳化铌
transition metal carbides
density functional theory(DFT)
band structures
density of state(DOS)
photoemission spectra
surface states
surface adsorption
