过渡金属碳化物(111)面电子结构的理论研究

采用第一性原理的密度泛函方法对过渡金属碳化物MC(111)清洁表面构型和电子结构进行系统研究.结果表明,与理想表面相比,表面弛豫导致表层金属原子和次表层碳原子分别朝体相和真空方向位移,从而导致层间距的收缩.由能带计算结果得知,紧邻或被EF穿越的活性表面态成分均为表面金属原子的dxz/dyz轨道.进一步考察了弛豫对表面态组成的影响,并对表面芯能级位移和功函进行了探讨.

Theoretical Studies on the Geometries and Electronic Structures of the (111 ) Surfaces of Transition-Metal Carbides

The geometries and electronic structures of the (111) surfaces of some transition metal carbides MC(M=Ti,Zr,V,Nb) have been investigated by using the first principle methods.The results indicate that,compared to the ideal surface,the first layer (metal layer) and second layer (carbon layer) shift inwards and outwards respectively,and as a result,the space between the first and second layer is contracted.The results of the band structure calculation show that the main components of the surface state in DOS located near or crossed by EF are dxz/dyz orbitals of the surface metal atoms,and the influence of the surface relaxation on this state has been studied.In addition,discussions about the surface core level shifts and the surface work functions are also presented.