AVS 57th International Symposium & Exhibition
    Surface Science Tuesday Sessions
       Session SS-TuA

Paper SS-TuA12
Ab Initio Calculations of the Preexponential Factor for the Diffusion of CO on Ag(001): The Importance of Inclusion of the Full Phonon Dispersion

Tuesday, October 19, 2010, 5:40 pm, Room Picuris

Session: Chemical Dynamics at Surfaces
Presenter: M. Alcántara Ortigoza, University of Central Florida
Authors: M. Alcántara Ortigoza, University of Central Florida
T.S. Rahman, University of Central Florida
K.P. Bohnen, Karlsruhe Institute of Technology, Germany
R. Heid, Karlsruhe Institute of Technology, Germany
Correspondent: Click to Email
Knowledge of factors that determine the diffusivity of CO on catalytic surfaces is of utmost importance for understanding why some surfaces render higher reaction rates (e.g. CO oxidation) than others. A rigorous calculation of the diffusion prefactor is not only the first approximation one should target to analyze diffusivity but also a prerequisite to adequately take into account dissipative anharmonic processes since calculation of both the prefactor and anharmonic processes rates require the full dispersion of all phonons in the system as input information. In this work, we obtain from first principles calculations the diffusion path of CO on Ag(001), the corresponding energy barrier, diffusion prefactors, and diffusion rate. The latter have been calculated via the total phonon density of states in the surface Brillouin zone from density functional perturbation theory calculations. Comparison of the results for the prefactors obtained using the full phonon dispersion curve with those confined only to the adsorbate modes on a frozen substrate point to significant differences and to the importance of having a knowledge of the full vibrational dynamics of the system, particularly at (low) temperatures which are relevant to experimental measurements.