The consecutive deposition of oxygen atoms on the Au(321) surface was studied by carrying out calculations based upon the spin polarized density functional theory within the GGA/PW91 exchange-correlation functional. The clean and oxygen covered Au(321) surfaces were modelled by using a periodic super-cell approach. The unit cell had 15 gold atoms, the outermost five defined the (111) terrace and the step. The adsorption of a single oxygen atom was more favourable if it occurred at a fcc hollow site on the (111) terrace adjacent to the step while for the co-adsorption of two oxygen atoms on the Au(321) surface, hollow sites near to the step were preferred. The introduction of an additional oxygen atom onto the already optimized slabs containing two oxygen atoms yielded, in some cases, structures with a single oxygen atom attached to the surface and an oxygen molecule far from the slab. In the other cases, several initial geometries converged to the same final structure and, in general, the adsorption of 3 oxygen atoms per unit cell was found to be thermodynamically unfavourable. The exception was a planar structure formed after reconstruction of the surface. The simultaneous adsorption of 4 oxygen atoms per unit cell was characterized by relatively high adsorption energies of −0.53 and −0.56eV; corresponding to a porous structure containing sub-surface oxygen atoms forming a gold oxide layer and to a well-ordered folded structure. The addition of a fifth oxygen atom to the structures already containing 4 oxygen atoms on the surface resulted in an endothermic process; suggesting that they would be hard to find even after exposure to high pressures of oxygen.

DFT Study of the Au(321) Surface Reconstruction by Consecutive Deposition of Oxygen Atoms. J.L.C.Fajín, M.Natália, D.S.Cordeiro, J.R.B.Gomes: Surface Science, 2008, 602[2], 424-35