Ab initio calculations of an M center on the AgBr(100) surface. Formation, electronic structure and spectrum of a primary Ag 2 cluster

Abstract

Ab initio calculations of the geometry, electronic structure, ionization and excitation energies of an M-center on the AgBr(100) surface are reported. This structure, formed in the process of surface reduction, may be viewed as an Ag 2 molecule adsorbed on the AgBr(100) surface with a “pit” and may become a primary center for photographic latent image formation. We found the equilibrium position of the Ag 2 molecule 0.62 Å above the surface and the adsorption energy 0.88 eV. The Σ g → Σ u excitation energies are greater by 0.6–1.0 eV and ionization potentials are 1.3–1.8 eV less than those for the free molecule. The results of the calculations which do and do not treat Ag 4d electrons explicitly match each other well. The adsorption energy is compared with that in other ab initio Ag n /AgBr(100) calculations.