The University of Southampton
University of Southampton Institutional Repository

Decomposition reactions of hexafluoropropylene oxide (HFPO): Rate coefficients calculated at different temperatures using ab initio and DFT reaction paths

Decomposition reactions of hexafluoropropylene oxide (HFPO): Rate coefficients calculated at different temperatures using ab initio and DFT reaction paths
Decomposition reactions of hexafluoropropylene oxide (HFPO): Rate coefficients calculated at different temperatures using ab initio and DFT reaction paths
A theoretical investigation has been carried out on the reaction mechanism and kinetics of the thermal decomposition of hexafluoropropylene oxide (HFPO), a compound of importance in fluorocarbon thin film preparation in the electronics industry. Decomposition occurs via two pathways, 1(a) to give CF2 and CF3C(O)F and 1(b) to give CF2O and CF3CF. Rate coefficients calculated for reaction 1(a) are reported over the temperature range 300–1500 K and compared with the small number of available rate coefficients at selected temperatures within this range. Rate coefficients are reported for the first time for reaction 1(b) over the temperature range 300–1500 K. The geometries of the stationary points on the potential energy surfaces have been obtained at the MP2/6-311++G(d,p) level, and the energies of selected points along the minimum energy path (MEP) have been improved at the RCCSD(T)/AVDZ and RCCSD(T)/AVTZ levels. These improved energies were extrapolated to the complete basis set limit to obtain RCCSD(T)/CBS//MP2/6-311++G(d,p) energies at each selected point on the MEP. The energies were then used in a dual-level direct dynamics method to calculate rate coefficients of the two decomposition reactions. The variational effect on the rate coefficients obtained is found to be small over the whole temperature range and tunnelling plays a small but significant role only at the lower temperatures. Comparison has been made of the computed reaction enthalpies, forward activation energies and rate coefficients computed at the RCCSD(T)/CBS//MP2/6-311++G(d,p) level with those computed with a number of different functionals and with the MP2 method. Reaction 1(a) is found to be the dominant reaction throughout the temperature range considered. Calculated rate coefficients for reaction 1(a) at the highest level used (improved canonical variational theory (ICVT) with small curvature tunnelling (SCT) with the RCCSD(T)/CBS//MP2/6-311++G(d,p) MEP) show reasonably good agreement with two recent sets of experimental values, although agreement with an older set is poor. This comparison highlights the need for more experimental rate coefficients for this thermolysis reaction over the whole temperature range considered, but particularly in the ranges 550–800 K and 1200–1500 K not currently covered by experimental measurements
0022-1139
29-37
Ng, Maggie
bc203fa1-3eb7-4b63-b1e9-78faca2e5c30
Mok, Daniel K.W.
49a4e516-0e71-4f59-a3ec-bd607b47ef33
Dyke, John M.
46393b45-6694-46f3-af20-d7369d26199f
Lee, Edmond P.F.
28f39876-705a-4fa5-b340-db5658ce1503
Ng, Maggie
bc203fa1-3eb7-4b63-b1e9-78faca2e5c30
Mok, Daniel K.W.
49a4e516-0e71-4f59-a3ec-bd607b47ef33
Dyke, John M.
46393b45-6694-46f3-af20-d7369d26199f
Lee, Edmond P.F.
28f39876-705a-4fa5-b340-db5658ce1503

Ng, Maggie, Mok, Daniel K.W., Dyke, John M. and Lee, Edmond P.F. (2014) Decomposition reactions of hexafluoropropylene oxide (HFPO): Rate coefficients calculated at different temperatures using ab initio and DFT reaction paths. Journal of Fluorine Chemistry, 159, 29-37. (doi:10.1016/j.jfluchem.2013.11.013).

Record type: Article

Abstract

A theoretical investigation has been carried out on the reaction mechanism and kinetics of the thermal decomposition of hexafluoropropylene oxide (HFPO), a compound of importance in fluorocarbon thin film preparation in the electronics industry. Decomposition occurs via two pathways, 1(a) to give CF2 and CF3C(O)F and 1(b) to give CF2O and CF3CF. Rate coefficients calculated for reaction 1(a) are reported over the temperature range 300–1500 K and compared with the small number of available rate coefficients at selected temperatures within this range. Rate coefficients are reported for the first time for reaction 1(b) over the temperature range 300–1500 K. The geometries of the stationary points on the potential energy surfaces have been obtained at the MP2/6-311++G(d,p) level, and the energies of selected points along the minimum energy path (MEP) have been improved at the RCCSD(T)/AVDZ and RCCSD(T)/AVTZ levels. These improved energies were extrapolated to the complete basis set limit to obtain RCCSD(T)/CBS//MP2/6-311++G(d,p) energies at each selected point on the MEP. The energies were then used in a dual-level direct dynamics method to calculate rate coefficients of the two decomposition reactions. The variational effect on the rate coefficients obtained is found to be small over the whole temperature range and tunnelling plays a small but significant role only at the lower temperatures. Comparison has been made of the computed reaction enthalpies, forward activation energies and rate coefficients computed at the RCCSD(T)/CBS//MP2/6-311++G(d,p) level with those computed with a number of different functionals and with the MP2 method. Reaction 1(a) is found to be the dominant reaction throughout the temperature range considered. Calculated rate coefficients for reaction 1(a) at the highest level used (improved canonical variational theory (ICVT) with small curvature tunnelling (SCT) with the RCCSD(T)/CBS//MP2/6-311++G(d,p) MEP) show reasonably good agreement with two recent sets of experimental values, although agreement with an older set is poor. This comparison highlights the need for more experimental rate coefficients for this thermolysis reaction over the whole temperature range considered, but particularly in the ranges 550–800 K and 1200–1500 K not currently covered by experimental measurements

Full text not available from this repository.

More information

Published date: March 2014
Organisations: Chemistry, Computational Systems Chemistry

Identifiers

Local EPrints ID: 362930
URI: http://eprints.soton.ac.uk/id/eprint/362930
ISSN: 0022-1139
PURE UUID: bbe04f96-1f55-481c-8ad5-95b37e9ce113
ORCID for John M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X

Catalogue record

Date deposited: 14 Mar 2014 16:39
Last modified: 20 Jul 2019 01:27

Export record

Altmetrics

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.

×