New potential energy surface for the CH/sub 3/+H/sub 2/bold-arrow-left-rightCH/sub 4/+H reaction: Calibration and calculations of rate constants and kinetic isotope effects by variational transition state theory and semiclassical tunneling calculations

Journal Article · Tue Dec 15 04:00:00 EST 1987 · J. Chem. Phys.; (United States)

OSTI ID:5954758

Joseph, T; Steckler, R; Truhlar, D G

We present a sequence of three successively improved new semiempirical potential energy surfaces for the reaction CH/sub 3/+H/sub 2/..-->..CH/sub 4/+H. The semiempirical calibration is based on ab initio electronic structure calculations and experimental thermochemical data, vibrational frequencies, reaction rate constants, Arrhenius parameters, and kinetic isotope effects (KIE's). To compare to the experimental kinetic data we apply variational transition state theory and semiclassical estimates of tunneling probabilities. We also provide detailed factorization analyses of the KIE's to illustrate the way in which various surface features contribute to the overall KIE's, and we discuss the substantial difficulties in attributing specific kinetic results to isolated potential energy surface features. Each of the three new surfaces, called J1, J2, and J3, has a thinner barrier than the one before. In addition, we provide one example, called surface J2A, showing the effect of making the barrier even thinner than on the best surface. The best surface yields rate constants for the forward and reverse reaction, activation energies, and KIE's that are consistent with most of the available experimental data.

• Research Organization: Department of Chemistry, University of Minnesota,Minneapolis, Minnesota 55455
• OSTI ID: 5954758
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 87:12; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKYL RADICALS
CHEMICAL REACTION KINETICS
ELEMENTS
ENERGY
HYDROGEN
ISOTOPE EFFECTS
KINETICS
METHYL RADICALS
NONMETALS
POTENTIAL ENERGY
RADICALS
REACTION KINETICS