TITLE

Concerted hydrogen atom exchange between three HF molecules

AUTHOR(S)
Komornicki, Andrew; Dixon, David A.; Taylor, Peter R.
PUB. DATE
February 1992
SOURCE
Journal of Chemical Physics;2/15/1992, Vol. 96 Issue 4, p2920
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
We have investigated the termolecular reaction involving concerted hydrogen exchange between three HF molecules, with particular emphasis on the effects of correlation at the various stationary points along the reaction. Using an extended basis, we have located the geometries of the stable hydrogen-bonded trimer, which is of C3h symmetry, and the transition state for hydrogen exchange, which is of D3h symmetry. The energetics of the exchange reaction were then evaluated at the correlated level, using a large atomic natural orbital basis and correlating all valence electrons. Several correlation treatments were used, namely, configuration interaction with single and double excitations, coupled-pair functional, and coupled-cluster methods. We are thus able to measure the effect of accounting for size-extensivity. Zero-point corrections to the correlated level energetics were determined using analytic second derivative techniques at the self-consistent field (SCF) level. Our best calculations, which include the effects of connected triple excitations in the coupled-cluster procedure, indicate that the trimer is bound by 9±1 kcal/mol relative to three separated monomers, in excellent agreement with previous estimates. The barrier to concerted hydrogen exchange is 15 kcal/mol above the trimer, or only 4.7 kcal/mol above three separated monomers. Thus the barrier to hydrogen exchange between HF molecules via this termolecular process is very low.
ACCESSION #
7630814

 

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