Nonstatistical effects and detailed balance in quasiclassical trajectory calculations of the thermal rate coefficient for O+OH. -->. O/sub 2/+H

Journal Article · Sun Jun 01 04:00:00 EDT 1986 · J. Chem. Phys.; (United States)

OSTI ID:5771929

Miller, J A

A detailed theoretical investigation of dynamical effects in the thermal rate coefficient for the title reaction is reported. Quasiclassical trajectory (QCT) calculations in both the forward (+1) and reverse (-1) directions are employed in the analysis. The results are compared with each other, with the variational transition state theory (VTST) calculations of Rai and Truhlar, with previous trajectory results for the reverse reaction, and with experiment. It is found that nonstatistical, or non-RRKM, ''recrossing'' effects play an important role in determining the thermal rate coefficient (the nonstatistical correction is almost a factor of 4 at 2500 K and nearly a factor of 2 even at 200 K). The results from the two trajectory methods satisfy detailed balance at high temperature, but at low temperature (250--300 K) the (-1) trajectories (through the equilibrium constant) predict a rate coefficient for the title reaction that is higher than that predicted by the (+1) method by about a factor of 2. This discrepancy is attributed to the crude handling of quantum effects near threshold in the (-1) trajectory method. The predictions of the (+1) method are in excellent agreement with experiment over the entire temperature range where experimental results are available (250--2500 K). At high temperatures (T>500 K) the VTST results of Rai and Truhlar predict accurately the rate of formation of HO(/sub 2/ complexes, but at lower temperatures the VTST and trajectory results are in disagreement. The VTST calculations are unable to predict the thermal rate coefficient of the title reaction at any temperature for a combination of reasons.

• Research Organization: Combustion Research Facility, Sandia National Laboratories, Livermore, California 94550
• OSTI ID: 5771929
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 84:11; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMBUSTION
ELEMENTS
HIGH TEMPERATURE
HYDROXYL RADICALS
KINETICS
NONMETALS
OXIDATION
OXYGEN
RADICALS
REACTION KINETICS
THERMOCHEMICAL PROCESSES