Structure and electronic properties of the surface of alkali metal peroxides

The CRYSTAL09 program with the implemented B3PW hybrid density functional in a localized basis of atomic orbitals is used to determine the atomic and electronic structure of the surface of lithium, sodium, and potassium peroxides. Geometric parameters, surface energies, partial densities of states, electron density distributions, overlap populations, and atomic charges are calculated. It is found that the geometry relaxation has a characteristic depth up to ～10 Å, while the surface states are located in the upper layers at a depth up to ～2.5 Å. Structural displacements of atoms do not exceed ～ 0.2 Å; the charge of the upper surface layers is positive, whereas the energy state shifts relative to the bulk ones can reach ～1 eV. The surface energy of peroxides decreases with an increase in the atomic number of the cation.