A theoretical study of oxidation on copper (100) surface
The further oxidations to subsurface of the 0.5 ML oxygen coverage copper (100) surface and MRR surface were investigated by DFT calculations. The two possible pathways for continuous oxidation on MRR and the c(2x2) phase could be separated into three parts: the adsorption of oxygen molecule, the dissociation of oxygen molecule and the oxygen atoms diffusion into subsurface. The missing row of MRR can be regarded as an active site for the adsorption and dissociation of oxygen molecule. The overall energy barriers of the two pathways of MRR and the c(2x2) phase are 0.75 and 0.9 eV respectively, which indicates that MRR is more likely to be oxidized to the subsurface. The convex hull analysis agrees with the three relatively stable surfaces of early oxidation in the previous experiments and the convex hull analysis further indicated that a special unit in both MRR and MRR-like surface may be the key element to the stability.