Surface sp half-metallicity of zinc-blende calcium monocarbide

Recent studies by Gao [Phys. Rev. B 75, 174442 (2007)] indicate zinc-blende CaC, SrC, and BaC exhibit robust sp half-metallic ferromagnetism with Curie temperatures higher than room temperature. Here we further investigate the surface electronic and magnetic properties of CaC by using the first-principles full-potential linearized augmented plane-wave method. The (001) surfaces terminated with Ca and C, respectively, and the (110) surface terminated with both Ca and C are considered. We discuss the surface stabilities from the calculated relaxed surface energies. Electronic structure calculations indicate that the half-metallicity is destroyed for both the Ca- and C-terminated (001) surfaces; however, the (110) surface preserves the half-metallic characteristic of the bulk CaC. We further reveal that the atomic magnetic moments of the (001) surfaces are greatly different from the bulk values, but the difference of atomic magnetic moments between the (110) surface and the bulk CaC is very small.