First-principle study on bulk and (1 1 1) surface of MP (M = K and Rb) in rocksalt structure

•The half metallic properties of rocksalt-type KP and RbP are studied.•The Slater-Pauling behaviours, energy levels and fat-bands of them are discussed.•The properties to KP's and RBP's (1 1 1) surfaces have been investigated.•The stabilities of bulk compounds and surfaces are studied.

The electronic and magnetic properties of bulk and (1 1 1) surfaces for MP (M = K and Rb) in rocksalt structure have been investigated by employing first-principle calculations. The results reveal that the compounds are half-metallic ferromagnets at the equilibrium lattice constants with large half-metallic band gaps of 0.46 and 0.74 eV. The (1 1 1) surfaces of KP and RbP keep their bulk half-metallic property. We study the stabilities of the bulk compounds and their (1 1 1) surfaces as well. The results show that those bulk compounds are more stable in the rocksalt structure than in the tetragonal structure. In addition, the K- and Rb-terminated surfaces are more stable than their P-terminated surfaces.