Nitric oxide chemisorption on nickel(111): coverage effects, site preferences, and adsorption geometry

Abstract

Several possible rationales for the different NO adsorption states observed on a Ni(111) surface are discussed, based on tight binding calculations of the extended Hueckel type. In the two fold bridge site, as the coverage of NO increases, for perpendicular adsorbed NO the N-O bonding increases and N-Ni bonding decreases. For slightly bent NO at low coverage and perpendicular NO at high coverage the same trends are obtained. These trends are consistent with the observed N-O, N-Ni stretching frequency change. At coverage 1/3, and in the perpendicular geometry, both N-O bonding and N-Ni bonding increase when NO changes adsorption sites from threefold to twofold or from two fold to on-top. In the on-top site it is calculated that both N-O bonding and N-Ni bonding increase when NO changes geometry from bent to perpendicular. In the twofold bridge site the effect of bending is to produce similar but smaller trends. 30 references, 7 figures, 7 tables.