VC(001)弛豫表面构型与电子结构第一性原理研究

A first principle study on the geometry and the electronic structures of VC(001) relaxed surface

用第一性原理方法对VC(0 0 1)清洁表面的构型和电子结构进行了详细研究 ,与TiC(0 0 1)面类似 ,VC(0 0 1)面弛豫后形成表面皱褶 ,其表层V原子和C原子分别朝体相和真空方向移动 .能带计算结果表明 ,过渡金属碳化物(0 0 1)面的能带结构符合刚性带理论模型 .对于VC(0 0 1)面 ,表面态主要处在 - 3 0eV附近 ,其主要成分为表层C原子的 2pz轨道 .此外 ,以表层V原子的 3d轨道成分为主的表面态出现在费米能级附近 ,由于这些表面态以表面法线方向的轨道 (3d2 z和 3dxz dyz)为主要成分 ,因此在表面反应中将起到重要作用 ,从而体现出与TiC(0 0 1)面不同的反应性质 .

By using the first principle method, the geometry and electronic structures of the clean VC(001) surface are investigated. Similar to the TiC(001) surface, the relaxation of the VC(001) surface leads to the C and V atoms on the top layer move outward and inward, respectively. Results of band structure calculation show that the band structures of transition metal (001) surfaces can be well described by the rigid barid model. For the VC(001) surface, the surface states are mainly located around 3.0eV below the Fermi level, and mainly originate from the 2p(z) orbital of C atom in the top layer. In addition, the surface states derived from the top layer V 3d orbitals are also observed near the Fermi level. Since these states contain significant contributions of those 3d orbitals vertical to the surface ( 3d(z)(2) and 3d(xz)/d(yz)), which will play important roles in the surface reactions, it could be expected that the VC(001) surface exhibits different surface reactivity compared with the TiC(001) surface.