abstract
The adsorption of CO on Mg(001) constitutes a challenge for current density functional approximations because of its weak interaction character. In the present work we show that the M06-2X and M06-HF exchange-correlation functionals are the first ones to provide a simultaneously satisfactory description of adsorbate geometry, vibrational frequency shift, and adsorption energy of CO on MgO(001). For a sufficiently large embedded cluster model, the three functionals of the M06 family-which contain a nonzero percentage of Hartree-Fock exchange (M06, M06-2X, and M06-HF)-all predict positive C-O vibrational shifts, in agreement with the experimental findings, while the local M06-L functional gives large negative shifts. Moreover, the shifts computed with the M06-2X and M06-HF potentials are in good agreement with the experimental shift of + 14 cm(-1). The interaction energy (D(e)) calculated with M06-2X and M06-HF is similar to 6.0 kcal/mol, which agrees well with the D(e) value (similar to 4 kcal/mol) deduced from the D(0) obtained in thermal desorption measurements on single-crystal surfaces. (C) 2008 American Institute of Physics.
keywords
HARTREE-FOCK CALCULATIONS; ADSORBED CARBON-MONOXIDE; CLUSTER MODEL; BONDING MECHANISM; MGO SURFACES; 1ST-PRINCIPLES DETERMINATION; VIBRATIONAL FREQUENCY; PALLADIUM CLUSTERS; CORRELATION-ENERGY; MGO(100) SURFACE
subject category
Chemistry; Physics
authors
Valero, R; Gomes, JRB; Truhlar, DG; Illas, F
our authors
José R. B. Gomes
Principal Researcheracknowledgements
Financial support was provided by the Spanish Ministry of Education and Science (Grant Nos. CTQ2005-08459CO2-01, UNBA05-33-001, and CTQ2005-03222) and by Generalitat de Catalunya 2005SGR-00697 grant. This work was supported in part by the National Science Foundation under Grant No. CHE-0704974.