Embedded density functional approach for calculations of adsorption on ionic crystals

We present an embedded density functional approach to study adsorption on crystalline surfaces. Following ideas suggested by Cortona, Wesolowski, and Warshel, we divide the total system into a quantum cluster and the surrounding lattice whose density is assumed to be the same as in the ideal crystal. In this case the Kohn–Sham Hamiltonian for electrons in the cluster contains additional terms corresponding to the Coulomb, exchange, correlation, and ‘‘nonadditive kinetic energy’’ potentials from the environment. Test calculations for the He and Ar dimers, X–H₂O molecular complexes (X=Li⁺, Na⁺, K⁺, F⁻ or Cl⁻) and water adsorption on the (001) surface of the NaCl crystal suggest that this model provides a promising alternative for cluster models employed earlier for calculations of defects and adsorption on ionic crystals.