Variational transition state theory and tunneling calculations of potential-energy-surface effects on the reaction of O(3p) with H/sub 2/

Technical Report · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5680981

Truhlar, D G; Garrett, B C

Rate constants for the important combustion O(3P state) + H/sub 2/ yield OH + H are calculated using variational transition state theory (VTST) with adiabatic and least-action ground-state transmission coefficients (VTST/G). Five different potential energy surfaces were considered and rates were computed for temperatures from 200 to 1400 K. First, collinear VTST/G calculations were compared with accurate quantum-mechanical ones to assess the accuracy of the dynamical and energetic approximations, which include the no-recrossing assumption of generalized transition state theory, semiclassical methods for tunneling calculations, and a Morse approximation for quantizing the generalized-transition state theory, stretching vibrations. For all five surfaces, which show widely different behavior, the calculations with the least-action ground-state transmission coefficients agree with the accurate quantal results within a factor of 2.9 in all cases. Next the three-dimensional VTST/G calculations were compared with experiment in an attempt to assess the validity of the potential energy surfaces. From this work, only one of the five surfaces could be definitively eliminated. The three-dimensional reaction was found to be dominated by tunneling at room temperature and nearby for all five surfaces. For the calculations on the most accurate ab initio potential energy surface, 60% of the ground-state reaction proceeds by tunneling even at 400 K.

• Research Organization: Chemical Dynamics Corp., Columbus, OH (USA)
• OSTI ID: 5680981
• Report Number(s): AD-A-163936/8/XAB
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
CHEMICAL REACTIONS
COMBUSTION
DYNAMICS
ELEMENTS
ENERGY
HYDROGEN
KINETICS
MECHANICS
NONMETALS
OXIDATION
OXYGEN
POTENTIAL ENERGY
REACTION KINETICS
SURFACES
THERMOCHEMICAL PROCESSES