Structure and optical properties of Na clusters deposited on MgO(001)

We present a hierarchical model for describing Na clusters which interact with a MgO(001) surface. The clusters are treated by time-dependent density-functional theory in full detail and the substrate by classical dynamics of Mg and O ions including dynamical polarizability. The model is calibrated to accurate all-electron density-functional model calculations of a Na adsorbate on an extended model of the MgO(001) surface. We show first applications to structure and optical response of Na_NMgO adsorption complexes for N = 3...8. The overall shape of the metal clusters is hardly changed by the interaction of the cluster with the surface while the detailed structure is slightly distorted to accommodate surface corrugation. The peak positions of the Mie plasmon resonances are not shifted, but the spectral fragmentation is strongly influenced by the surface.