title: Size-dependent binding energies of methane to small gold clusters.
abstract: The reactions of small gold cluster cations Au(x)(+) (x=2-6) with CH(4) were studied by joint gas-phase kinetics and first-principles density functional theory calculations. The experimentally obtained temperature-dependent low pressure rate constants were analyzed by employing the Lindemann energy transfer model for association reactions in conjunction with statistical RRKM theory. In this way cluster-size-dependent binding energies of methane to the gold cluster cations were determined from the experimental data for two different transition-state models. The experimental binding energies obtained by employing a "loose" transition-state model are in good agreement with the theoretical values at the optimal adsorption geometries, while a "tight" transition-state model clearly gives a lower limit for the binding energies. Additionally, Kohn-Sham molecular orbitals of Au(x)-CH(4)(+) are presented to gain detailed insight into the cluster-methane bonding mechanism.
authors.affiliation: Institute of Surface Chemistry and Catalysis, University of Ulm, Albert-Einstein-Allee 47, 89069 Ulm, Germany.
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Lang
authors.forename: Thorsten M
authors.initials: TM
authors.lastname: Bernhardt
authors.forename: Robert N
authors.initials: RN
authors.lastname: Barnett
authors.forename: Uzi
authors.initials: U
authors.lastname: Landman
mesh_terms: D000327:Adsorption; D001665:Binding Sites; D003198:Computer Simulation; D006046:Gold / Q000737:chemistry*; D007700:Kinetics; D008697:Methane / Q000737:chemistry*; D008956:Models, Chemical; D010316:Particle Size; D013499:Surface Properties
chemical_list: D006046:Gold; D008697:Methane