title: The (1 X 1) --> hexagonal structural transition on Pt(100) studied by high-energy resolution core level photoemission.
abstract: The (1 X 1) --> quasihexagonal (HEX) phase transition on a clean Pt(100) surface was investigated by monitoring the time evolution of the Pt4f(72) core level photoemission spectra. The spectral component originating from the atoms forming the (1x1) metastable unreconstructed surface was found at -570+/-20 meV with respect to the bulk peak. Ab initio calculations based on density functional theory confirmed the experimental assignment. At temperatures above 370 K, the (1 X 1) phase irreversibly reverts to the more stable HEX phase, characterized by a surface core level shifted component at -185 +/ -40 meV. By analyzing the intensity evolution of the core level components, measured at different temperatures in the range of 393 - 475 K, we determined the activation energy of the phase transformation, E = 0.76 +/- 0.04 eV. This value is considerably lower than the one previously determined by means of low energy electron diffraction. Possible reasons for this discrepancy are discussed.
authors.affiliation: Physics Department and Center of Excellence for Nanostructured Materials, Trieste University, Via Valerio 2, I-34127 Trieste, Italy Laboratorio TASC INFM-CNR, I-34012 Trieste, Italy. alessandro.baraldi@elettra.trieste.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Baraldi
authors.forename: Erik
authors.initials: E
authors.lastname: Vesselli
authors.forename: Laura
authors.initials: L
authors.lastname: Bianchettin
authors.forename: Giovanni
authors.initials: G
authors.lastname: Comelli
authors.forename: Silvano
authors.initials: S
authors.lastname: Lizzit
authors.forename: Luca
authors.initials: L
authors.lastname: Petaccia
authors.forename: Stefano
authors.initials: S
authors.lastname: de Gironcoli
authors.forename: Andrea
authors.initials: A
authors.lastname: Locatelli
authors.forename: T Onur
authors.initials: TO
authors.lastname: Mentes
authors.forename: Lucia
authors.initials: L
authors.lastname: Aballe
authors.forename: Jonas
authors.initials: J
authors.lastname: Weissenrieder
authors.forename: Jesper N
authors.initials: JN
authors.lastname: Andersen