First-Principles Study of Adsorption of Atomic Oxygen on PdZn(111) Surface.

The adsorption structure of atomic oxygen on the PdZn(111) surface is studied using the first-principles calculation. At lower coverages up to 0.5 ML, oxygen atoms prefer to adsorb at threefold hollow sites surrounded by two Zn atoms and a Pd atom. Surface Zn atoms bonded with adsorbed oxygen atoms move toward the vacuum region, and the maximum displacement has reached 0.1nm at 0.375 ML. At higher coverages from 0.625ML to 1.0 ML, some oxygen atoms intruded into the surface layer and formed bonds with the Zn atoms in the second layer. At 0.75 ML, we observed the formation of the Zn-O hexagonal rings on the surface layer. It seems that the formation of the hexagonal rings largely contributes to the stability of the surface layer. However, the surface DOS and H₂O adsorption indicate no essential difference owing to the hexagonal Zn-O rings, and the hexagonal Zn-O rings disappeared at higher coverages. We discussed the relation of the adsorption energy, coverage, and the number of atoms located in the vicinity of the adsorbed oxygen atoms. [ABSTRACT FROM AUTHOR]