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 has 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 atoms which are located within this area clearly exhibit electronic properties which are different of those of a pure nickel surface. The main modification is related to their electronic population: it decreases by 0.17 electrons due to a reorganization of the electron density of states involving the highest-occupied (HO) and lowest-unoccupied (LU) contributions. As soon as the K influence areas begin to overlap (this is achieved for a coverage: theta(K) = 0.04 K/Ni), all the Ni surface atoms have a common K-modified electronic structure. This structure could be related to a peculiar chemical reactivity of these Ni surface atoms, by comparison with those of the clean surface.