Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/17260
Title: DFT and AB initio calculations on two reactions between hydrogen atoms and the fire suppressants 2-H heptafluoropropane and CF3Br
Authors: Lee, EPF
Dyke, JM
Chow, WK 
Chau, FT
Mok, DKW 
Keywords: 2-H heptafluoropropane
Ab initio calculations
Barrier heights
Density functional calculations
Issue Date: 2007
Source: Journal of computational chemistry, 2007, v. 28, no. 9, p. 1582-1592 How to cite?
Journal: Journal of Computational Chemistry 
Abstract: Reaction enthalpies and barrier heights of the reactions CF3Br + H → CF3 + HBr {reaction (1)) and CF3CHFCF 3 + 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 ah initio benchmarks for both reactions (1) and (2), the MPWBIK 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 CF3CFCF 3 calculated at the near state-of-the-art level has a value of -(318 ± 3) kcal/mole.
URI: http://hdl.handle.net/10397/17260
ISSN: 0192-8651
DOI: 10.1002/jcc.20695
Appears in Collections:Journal/Magazine Article

Access
View full-text via PolyU eLinks SFX Query
Show full item record

SCOPUSTM   
Citations

13
Last Week
0
Last month
0
Citations as of Nov 18, 2017

WEB OF SCIENCETM
Citations

12
Last Week
0
Last month
0
Citations as of Nov 15, 2017

Page view(s)

95
Last Week
1
Last month
Checked on Nov 19, 2017

Google ScholarTM

Check

Altmetric



Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.