Comparative study of the reaction dynamics of several potential energy surfaces of O(/sup 3/P)+H/sub 2/. -->. OH+H. I
Two new potential energy surfaces for th O+H/sub 2/..-->..OH+H reaction are presented, and a detailed comparision of the saddle point properties and thermal rate constants of these and of six other O+H/sub 2/ surfaces is made. The two new surfaces are (1) an extended BEBO surface and (2) a rotated-Morse-oscillator-spine (RMOS) fit to the accurate ab initio POLCI surface of Walch and Dunning. In the BEBO surface, an improved end atom repulsive potential is used which leads to a much more accurate barrier estimate (11.52 kcal/mol) than with the usual anti-Morse expression. The POLCI--RMOS surface is an essentially quantitative fit to the ab initio points, and has a barrier of 12.58 kcal/mole. The other O+H/sub 2/ surfaces examined include the LEPS surface of Westenberg and de Haas (LEPS-WDH) and of Johnson and Winter (LEPS-JW), the diatomics-in-molecules (DIM) surface of Whitlock, Muckerman, and Fisher, the ab initio surface of Howard, McLean, and Lester (HML), and a fit to HML's surface by Schinke and Lester (SL). For the LEPS-JW and SL surfaces, the quasiclassical trajectory (QCT) and Wigner corrected transition state theory (TST) rate constants are in excellent agreement with each other over the 300--2000 K range. There is, however, poor agreement between the QCT and TST rate constants for the DIM surface. This is apparently due to the more product-like location of the saddle point on that surface. Using both the QCT and TST results to make best estimates of the true O+H/sub 2/ rate constants, we find that the LEPS-JW, DIM, and POLCI rate constants all agree with experiment within the experimental uncertainties. Although the treatment of multiple surface and spin-orbit effects does introduce some uncertainty into this analysis, the experimental uncertainties are large enough to enable agreement with experiment almost irrespective of which electronic weighting factor is used.
- Research Organization:
- Department of Chemistry, Northwestern University, Evanston, Illinois 60201
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 6400064
- Journal Information:
- J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 74:9; ISSN JCPSA
- Country of Publication:
- United States
- Language:
- English
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