Atomic and molecular forms of oxygen on Ag(331). Theoretical analysis using the DFT method

Abstract

Oxygen adsorption on Ag(331) is analyzed in a cluster approximation using the density functional theory (DFT) method. Adsorption centers (AC) for the bridge (S2) and three-center (S3) coordinations of oxygen are identified on the stepwise face Ag(331) and the Ag-O bond energies at these centers are calculated. For atomic adsorption, the Ag-O bond strength varies from 50 to 65 kcal/mole, depending on AC. The heat of molecular adsorption DH = 5 kcal/mole for S2(L1-L2) type AC. The molecule is oriented parallel to Ag(110) between the terraces with R(O-O) = 1.34 a Calculations showed that the ground state of the O2Ag20(331) system is a triplet, but a part of spin density is delocalized on silver atoms, so that the spin density on oxygen ρs(O) = 0.46 (ρs = 1.0 for the free O2 molecule). The energy of the singlet state is 9 kcal/mole greater than that of the ground state.