The University of Southampton
University of Southampton Institutional Repository

DFT and ab initio calculations on two reactions between hydrogen atoms and the fire suppressants 2-H heptafluoropropane and CF3Br

Record type: Article

Reaction enthalpies and barrier heights of the reactions CF3Br + H CF3 + HBr {reaction (1)} and CF3CHFCF3 + H CF3CFCF3 + H2 {reaction (2)} have been calculated at the near state-of-the-art ab initio level, and also by employing the B3LYP, BH&HLYP, BB1K, MPW1K, MPWB1K and TPSS1KCIS functionals. In addition, the integrated molecular orbital + molecular orbital (IMOMO) method has been used to study reaction (2). The ab initio benchmark values of the reaction enthalpy (298 K) and barrier height (0 K) of reaction (2) are reported for the first time {-(0.7 ± 0.7) and 13.3 ± 0.5 kcal/mole respectively}. When density functional theory (DFT) results are compared with ab initio benchmarks for both reactions (1) and (2), the MPWB1K functional is found to have the best performance of the six functionals used. The IMOMO method with the RCCSD/aug-cc-pVTZ and/or RCCSD(T)/aug-cc-pVTZ levels, as the high levels of calculation on the model system, gives reaction enthalpies and barrier heights of reaction (2), which agree with ab initio benchmark values to within 1 kcal/mole. Computed key geometrical parameters and imaginary vibrational frequencies of the transition state structures of reactions (1) and (2) obtained at different levels of calculation are compared. The magnitudes of the computed imaginary vibrational frequencies of the transition states of both reactions considered are found to be very sensitive to the levels of calculation used to obtain them. The heat of formation (298 K) of CF3CFCF3 calculated at the near state-of-the-art level has a value of -(318 ± 3) kcal/mole.

Full text not available from this repository.

Citation

Lee, E.P.F., Dyke, J.M., Chow, W.K., Chau, F.T. and Mok, D.K.W. (2007) DFT and ab initio calculations on two reactions between hydrogen atoms and the fire suppressants 2-H heptafluoropropane and CF3Br Journal of Computational Chemistry, 28, (9), pp. 1582-1592. (doi:10.1002/jcc.20695).

More information

Published date: 2007
Keywords: barrier, density functional calculations, molecular-orbital imomo, heights, kinetics, photodetachment, energies, basis-sets, transition-state, density-functional theory, spectroscopy, ab initio calculations, abstraction, thermochemical, barrier heights, 2-h heptafluoropropane

Identifiers

Local EPrints ID: 54329
URI: http://eprints.soton.ac.uk/id/eprint/54329
ISSN: 1096-987X
PURE UUID: cdf0ff65-96e5-4d60-b3f0-ca7eaf1d2372
ORCID for J.M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X

Catalogue record

Date deposited: 31 Jul 2008
Last modified: 17 Jul 2017 14:35

Export record

Altmetrics

Contributors

Author: E.P.F. Lee
Author: J.M. Dyke ORCID iD
Author: W.K. Chow
Author: F.T. Chau
Author: D.K.W. Mok

University divisions


Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×