A THEORETICAL-STUDY OF THE ELECTRONIC-PROPERTIES OF A NICKEL(111) SURFACE PARTIALLY COVERED BY POTASSIUM ADATOMS

The recursion method involving a Hamiltonian of extended Huckel type h as been used for determining the electronic properties of the various nickel atoms of a Ni(111) surface with potassium atoms deposited on it . It has been found that each K adatom has, on the Ni surface atoms, a circular influence area with a radius of about 6 angstrom. The Ni ato ms which are located within this area clearly exhibit electronic prope rties which are different of those of a pure nickel surface. The main modification is related to their electronic population: it decreases b y 0.17 electrons due to a reorganization of the electron density of st ates involving the highest-occupied (HO) and lowest-unoccupied (LU) co ntributions. As soon as the K influence areas begin to overlap (this i s achieved for a coverage: theta(K) = 0.04 K/Ni), all the Ni surface a toms have a common K-modified electronic structure. This structure cou ld be related to a peculiar chemical reactivity of these Ni surface at oms, by comparison with those of the clean surface.