Theoretical study of adsorption of Cu, Ag, and Au on the NaCl(100) surface.

Abstract

The adsorption of noble metal atoms (Cu, Ag, and Au) on the NaCl(100) surface has been studied by means of an embedded cluster approach. We use different models for the surface in order to study the convergence of the properties participating in the bonding. The use of a suitable embedding and the lack of participation of the sodium $3s$ orbitals allows for reliable results with small clusters. Adsorption energies and metal-surface distances are calculated by using ab initio Hartree-Fock calculations and including the correlation energy at the second order of perturbation theory. An effective core potential approximation, which includes relativistic mass-velocity corrections for silver and gold, is used for the inner electrons of the metal. Corrections for the basis set superposition error are considered as well. The metal atoms are preferentially absorbed on the top of cationic sites. The interaction energy is small (\ensuremath{\approx}0.1 eV) and the distances long (g3 \AA{}) for all models considered. Adsorption has no noticeable chemical contributions. This is explained by resorting to the electronic structure of metal and surface. Most of the binding energy is due to electrostatic and dispersion forces.