ELECTRONIC-STRUCTURE OF OH ADSORBED ON NICKEL

In the ab initio version of the Hartree-Fock method, the forms of adsorption of OH on nikel have been analyzed, with the Ni(100), Ni(111), and Ni(110) surfaces modeled by minimum-size Ni8 clusters. The calculations took into account the electron correlation energy of the O-H bond within the framework of the Goddard generalized valence bond method. In the adsorption of OH on Ni(100) or Ni(111), a linear form of adsorption is realized, and on Ni(110) an angular form. In all cases, a considerable transfer of electron density from the metal to the OH was noted. Many-center bonds of OH with the surface are the most stable. For the OH/Ni(110) system, the calculations predict a stretching vibration frequency nu(a)(O-H) = 3300 cm-1, a bending vibration frequency delta(Ni-O-H) = 840 cm-1, a heat of adsorption E(OH) = 75 kcal/mole, an angle between the O-H bond and the normal to Ni(110) theta0 = 20-degrees, a work function 5.1 eV, and a width of the s-band 8.2 eV.