Magnetism of the Ni(110) and Ni(100) surfaces: Local-spin-density-functional calculations using the thin-slab linearized augmented-plane-wave method

Results of self-consistent local-spin-density-functional calculations are reported for the first time for the Ni(110) surface, represented by one-, three-, and five-layer slabs. Calculations for one- and five-layer slabs of Ni(100) are also reported. The behavior of the surface magnetization with varying slab thickness elucidates the nature and origin of the surface magnetic moment. We predict a 13% enhancement of the Ni(110) surface magnetic moment compared to the bulk value. For the Ni(100) surface, we find a smaller surface enhancement about 7%, compared to bulk, which agrees with the results of Jepsen et al. The enhancement of surface magnetic moments on Ni(100) and Ni(110) surfaces is attributed to $s-d$ dehybridization at the surface and to the presence of electrostatic shifts required to maintain layer-by-layer charge neutrality. We find that the total $d$-electron charge is the same in each layer, which contradicts the $\mathrm{sp}$-to-$d$ charge transfer found by Tersoff and Falicov at transition-metal surfaces. An exchange-split pair of very localized surface states is found on the Ni(110) surface, which is in good agreement with the photoemission measurements of Eberhardt et al. The theoretical exchange splitting, 0.6 eV, is twice as large as that found experimentally. This discrepancy is similar to that found for the bulk Ni bands and is attributed to neglected many-body effects. For Ni(100) it is found that surface states at the Brillouin-zone center are unable to account for the reversal above threshold of the spin polarization of photoemitted electrons, in agreement with other self-consistent calculations. A majority-spin ${\overline{\Sigma }}_2$ surface resonance on Ni(100) is in good agreement with the experimental surface state of Plummer and Eberhardt but has greater dispersion downward away from the Fermi energy than is found experimentally. We do not find the ${\overline{\Delta }}_1$ minority-spin surface-state band observed by Plummer and Eberhardt just below the Fermi energy; instead, we find a flat ${\overline{\Delta }}_2$ minority-spin surface-state band about 0.5 eV below the Fermi energy. Finally, we find surface core-level chemical shifts to reduced binding energy of 0.39 eV on Ni(100) and 0.45 eV on Ni(110). The polarization of the core states by the valence electrons splits the spin-up and spin-down core states in each layer by about 0.6 eV, thereby permitting, in principle at least, the experimental verification of these surface core-level shifts, since the two spin manifolds are separated.