V. K. Fedyanin

On the coverage dependence of chemisorption characteristics on metals

Abstract Within the composite Anderson-Ising Hamiltonian the coverage dependence of chemisorption characteristics like the chemisorption energy, the electron charge and magnetic moment localized at impurities (adsorbed atoms) and the impurity electron density of states are investigated. Calculations are carried out within the self-consistent unrestricted Hartree-Fock scheme for the electron component and within the Bragg-Williams approximation for the ionic adsorbate component. The dependence of the magnetic phase transition on the coverage is obtained. It is interpreted as a second-order phase transition with critical exponent s = 1 2 . The crossover problem in the phase space of the model parameters is also discussed.

Electron correlations in the chemisorption theory: Self-consistent calculations of the adatom charge

Abstract The single hydrogen-like adatom chemisorption on transition metal surfaces is studied by using the generalized model Hamiltonian. This Hamiltonian includes the possibility of influence of the adatom orbital occupancy on the charge transfer between the adatom and the substrate metal. The correlation effects were included up to second order in V (the single particle coupling strength). The numerical calculations of the charge transfer between an adatom and a substrate metal, as well as the comparison with results obtained for the standard Newns-Anderson model indicate that this generalized Hamiltonian can be more efficient in describing the chemisorption process.

Electron correlation effects in chemisorption theory at finite submonolayer coverages

Within the generalized Anderson-Newns Hamiltonian the coverage dependence of the chemisorption characteristics such as the adatom charge and adatom local density of states has been calculated. The electron correlation effects on the adatom were included up to second order in V (the single particle hopping strength between the adatom and the substrate) and the Bragg-Williams approximation for the ionic adsorbate component was used. For a model system of the hydrogen chemisorption on the transition metal surfaces a progressive neutralization of the adatoms with increasing coverage was obtained and all values of the adatom charge are much smaller than the corresponding ones calculated within the Hartree-Fock (HF) approach for general coverages or beyond HF for zero coverages.

Chemisorption at finite coverages—the coherent potential approximation vs the equation of motion for green's functions method

Abstract The electronic structure, chemisorption energy and adatom charge of the chemisorbed overlayer on a metal surface are studied within the model by the Newns Hamiltonian generalized to finite coverages. It is shown that the method of equation of motion for appropriate Greens function together with some decouplings of the higher-order Greens functions can be used in calculations of the overlayers electronic properties as an efficient and alternative way to the coherent potential approximation method.