CLUSTER-SIZE CONVERGENCE OF SOME PHYSICAL PARAMETERS OF BARE (NIN) AND CH3-CHEMISORBED (CH3-NIN) NICKEL (111) CLUSTERS - AN ABINITIO STUDY

Hartree-Fock calculations of the molecular geometry and electronic properties (ionization potentials) of bare Ni(n) clusters (n = 3, 7, 13, and 25) and nickel clusters bearing a chemisorbed CH3 radical are reported. A basis of double-zeta quality on light atoms including carbon and a model core potential along with double-zeta plus polarization auxiliary basis sets for nickel atoms have been used. Computed properties serve to assess cluster-size convergence when nickel atoms core electrons are described with [1s-3d] pseudopotentials. In spite of their simplicity, results with these potentials are in good agreement with previously reported theoretical and experimental data on seven-atom clusters. This suggests that the cluster-model approach to surface bonding using simple pseudopotentials can lead to meaningful results and tractable computational times when applied to larger chemisorbed organic molecules. Thus, this approach may be adequate to help find out direct experimental evidence of the interfacial bonding for grafted structures obtrained under cathodic electropolymerization of acrylonitrile on nickel surfaces.