Modelling of silver adhesion on MgO(100) surface with defects

We show how surface defects (especially F_s⁰ and V_s⁰ centres) can play a major role in the adhesion of Ag (at 1:4 and 1:1 coverages) on the MgO(100) surface. Our calculations use a periodic (slab) model and an ab initio Hartree-Fock approach with a posteriori electron correlation corrections. We are able to analyse the interatomic bond populations, effective charges and multipole moments of ions, in combination with the interface binding energy and the equilibrium distances. Both surface defects cause strong redistributions of the electron density which increase the binding energy of metal atoms by more than an order of magnitude. This implies radiation-induced strengthening of metal adhesion on oxide substrates and clarifies defect mechanisms in nucleating film growth. We compare our atomistic predictions with those from simpler methods which might be used for complex technologically interesting systems. There is good general agreement with the image interaction model; differences arise partly from different treatments of dispersion and partly from subtle but significant charge redistribution in the Ag. Further, a simple Born-Haber analysis of charge transfer is consistent with the several cases predicted in the atomistic calculations.