Photoinitiated reaction dynamics between aligned adsorbates on solid surfaces: A theoretical exploration of the H + CO2 system on LiF(001)

Josie V. Setzler, Hua Guo, George C Schatz

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Abstract

We report a quasi-classical trajectory study of a chemical reaction between H and CO2 at the LiF(001) surface. The reaction is initiated by photodissociation of well-aligned HBr(ad) at 193 nm, which produces a "hot" H atom directed toward a nearby CO2(ad). Single molecules of each reactant are placed on a static surface, and a full-dimensional HCO2 potential derived from ab initio calculations is used. The adsorbate-substrate and the adsorbate-adsorbate potentials consist of both nonelectrostatic and electrostatic contributions. Several energetically favorable adsorption configurations are determined by a Monte Carlo method. Quasi-classical trajectories are calculated at 80 K for four different adsorption configurations. We find that the reactivity at some configurations is significantly enhanced compared with the corresponding gas-phase simulation. The calculated impact parameters and incident angles of the surface-aligned collisions indicate that the enhanced reactivity can be largely attributed to the closeness and alignment of the coadsorbates on the surface. Owing to the long-lived complex, product distributions, with the exception of a departure angle, show little memory with regard to the initial configuration and are similar to those obtained in the gas phase. A significant number of the unreacted hydrogen atoms retain sufficient energy to make subsequent reaction with other coadsorbates a possibility. We find evidence of several dynamic features pertinent to the use of the surface as a template for reactivity enhancement, including scattering at the surface, the squeezed atom effect, chattering, and caging.

Original languageEnglish
Pages (from-to)5352-5361
Number of pages10
JournalJournal of Physical Chemistry B
Volume101
Issue number27
Publication statusPublished - Jul 3 1997

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Engineering(all)

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