Comparison of quantum dynamics and quantum transition state theory estimates of the H + CH4 reaction rate.

Andersson, Stefan, 1973 (author): Gothenburg University,Göteborgs universitet,Institutionen för kemi,Department of Chemistry

Nyman, Gunnar, 1957 (author): Gothenburg University,Göteborgs universitet,Institutionen för kemi,Department of Chemistry

Arnaldsson, Andri (author)

Manthe, Uwe (author)

Jónsson, Hannes (author)

(creator_code:org_t)

2009-03-10
2009
English.
In: The journal of physical chemistry. A. - : American Chemical Society (ACS). - 1520-5215 .- 1089-5639. ; 113:16, s. 4468-78

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Abstract Subject headings

Thermal rate constants are calculated for the H + CH(4) --> CH(3) + H(2) reaction employing the potential energy surface of Espinosa-Garcia (Espinosa-Garcia, J. J. Chem. Phys. 2002, 116, 10664). Two theoretical approaches are used. First, we employ the multiconfigurational time-dependent Hartree method combined with flux correlation functions. In this way rate constants in the range 225-400 K are obtained and compared with previous results using the same theoretical method but the potential energy surface of Wu et al. (Wu, T.; Werner, H.-J.; Manthe, U. Science 2004, 306, 2227). It is found that the Espinosa-Garcia surface results in larger rate constants. Second, a harmonic quantum transition state theory (HQTST) implementation of instanton theory is used to obtain rate constants in a temperature interval from 20 K up to the crossover temperature at 296 K. The HQTST estimates are larger than MCTDH ones by a factor of about three in the common temperature range. Comparison is also made with various tunneling corrections to transition state theory and quantum instanton theory.

By the author/editor: Andersson, Stefa ...; Nyman, Gunnar, 1 ...; Arnaldsson, Andr ...; Manthe, Uwe; Jónsson, Hannes

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