Molecular oxygen chemisorption on Ag(110) surface at long bridge (LB) site has beenstudied theoretically by use of cluster model (CM) and dipped adcluster model (DAM)for Ag6O2 system. Two low-lying states, ^1A1 and ^3A2, are obtained. The ^1A1 state corresponds th the O2^2^- species adsorption along [110] trough, while the ^3A2 state to the O2^- species along [001] direction. For the CM method, the calculated binding energies of the two states are much lower than the experimental data (even negative). With the DAM method, the adsorption system is stabilized to produce positive binding energies, which are remarkable close to the experimental value of 38.8 kJ/mol, and the [110] trough geometry is obviously preferred. The optimized adsorption geometries are in good agreement with the experimental results.

Key words: OXYGEN, SILVER, AB INITIO CALCULATION, ADSORPTION STATE, ADSORPTION ENERGY