Electronic structure of CaF2-type ZrO2 surface and bulk

Clean Zr-terminated and O-terminated surface systems of the CaF2-type ZrO2 were calculated by ab initio ‘mixed-basis+norm conserving non-local pseudopotential’ method. New gap states of Zr-terminated surface system appear below the bottom of conduction band of bulk ZrO2, which derive from the split of the d state due to the lower symmetry of crystal field around the Zr surface atoms. New gap states of O-terminated surface system appear above the top of the valence band, which may derive from the energy increase of surface atoms. The difference of density of states between the Zr-terminated and O-terminated surface systems suggests that the Zr-terminated surface system is more stable than the O-terminated surface system.