Using the first-principles method, the electronic structures of clean and hydrogen-adsorbed ZrC (111) surfaces have been studied. The results of the geometrical optimization indicate that, for the clean surface, the spacings between the adjacent layers are contracted and expanded alternately from the surface to the bulk within certain layers. The main components of the surface state in DOS located near E_F and 4d_(xz)/d_(yz) orbitals of the surface Zr atoms, and compared to the ideal surface, the relaxation of the surface has little influence on this state. For the hydrogen-adsorbed surface, the calculated results show that the hydrogen atoms are preferably adsorbed on the surface hollow sites in which the third layer Zr atoms sit directly below them, and in this case, the H 1s-induced state is separated from the bulk states. In addition, the variation of H 1s- induced sate is explained by comparing with the H/NbC(111) system, and the discussions about the surface core-level shifts and the surface work functions are also presented in the paper.

Key words: CARBIDE, SURFACE STATES, BAND STRUCTURES, ELECTRONIC STRUCTURE, ZIRCONIUM COMPOUNDS, NIOBIUM COMPOUNDS, ADSORPTION