title: Lifting of Ir{100} reconstruction by CO adsorption: an ab initio study.
abstract: The adsorption of CO on unreconstructed and reconstructed Ir{100} has been studied, using a combination of density functional theory and thermodynamics, to determine the relative stability of the two phases as a function of CO coverage, temperature, and pressure. We obtain good agreement with experimental data. At zero temperature, the (5 x 1) reconstruction becomes less stable than the unreconstructed (1 x 1) surface when the CO coverage exceeds a critical value of 0.09 ML. The interaction between CO molecules is found to be weakly repulsive on the reconstructed surface but attractive on the unreconstructed, explaining the experimental observation of high CO coverage on growing (1 x 1) islands. At all temperatures and pressures, we find only two possible stable states: 0.5 ML CO c(2 x 2) overlayer on the (1 x 1) substrate and the clean (5 x 1) reconstructed surface.
authors.affiliation: Thoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India.
authors.forename: Prasenjit
authors.initials: P
authors.lastname: Ghosh
authors.forename: Shobhana
authors.initials: S
authors.lastname: Narasimhan
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Jenkins
authors.forename: David A
authors.initials: DA
authors.lastname: King