Journal article
An assessment of the performance of high-level theoretical procedures in the computation of the heats of formation of small open-shell molecules
The Journal of Physical Chemistry A, Vol.106(34), pp.7927-7936
2002
Abstract
The heats of formation at 0 K (ΔfH0) of 29 small (containing up to 3 heavy atoms) open-shell molecules, with accurately known experimental values, have been calculated using a number of high-level theoretical procedures. The theoretical methods examined include variants of Gaussian-n (G2, G2-RAD(RMP2), G2-RAD(B3-LYP), G2-RAD(QCISD), G3, G3-RAD, G3X, G3X-RAD, G3(MP2), G3(MP2)-RAD, G3X(MP2) and G3X(MP2)-RAD), CBS (CBS-APNO, CBS-Q, CBS-RAD and CBS-QB3), and Martin extrapolation (Martin-2, Martin-3, W1, W1′, W1h, W2h and W2) procedures. The open-shell systems include doublet radicals (•BeH, •CH, •CH3, •NH2, •OH, •SiH3, •PH2, •SH, •N2+, •NO, •ONO, •O2-, •CN, •CO+,•CS+, •CCH, •CHO, •OOH, •CHCH2, •CH2CH3, •CH2OH, •OCH3, •SCH3 and •COCH3) and triplet biradicals (:CH2, :NH, :SiH2, :O2, and :S2). The results for these systems are used to assess the performance of the various theoretical methods. The smallest mean absolute deviations (MADs) from experiment are found with the G3-RAD, G3X-RAD, G3X, W1h, W2, W1, and W2h procedures with MADs lying in the range 2.0-2.5 kJ mol-1 The smallest values for the largest deviation (LD) from experiment are found with the G3X, G3X-RAD, W2, and W2h procedures and are ±6.4 kJ mol-1. A selection of the most accurate theoretical procedures (G3-RAD, G3X-RAD, G3X, W1h, W2, W1, and W2h) is used to predict the heats of formation for several radicals (•OF, •CH2CHCH2, •CH2CN, •CH2COOH, and •CH2C6H5) for which there are greater uncertainties associated with the experimental values.
Details
- Title
- An assessment of the performance of high-level theoretical procedures in the computation of the heats of formation of small open-shell molecules
- Authors/Creators
- D.J. Henry (Author/Creator)C.J. Parkinson (Author/Creator)L. Radom (Author/Creator)
- Publication Details
- The Journal of Physical Chemistry A, Vol.106(34), pp.7927-7936
- Publisher
- American Chemical Society
- Identifiers
- 991005543925707891
- Copyright
- © 2002 American Chemical Society
- Murdoch Affiliation
- Murdoch University
- Language
- English
- Resource Type
- Journal article
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- Citation topics
- 2 Chemistry
- 2.15 Physical Chemistry
- 2.15.3 Quantum Chemistry
- Web Of Science research areas
- Chemistry, Physical
- Physics, Atomic, Molecular & Chemical
- ESI research areas
- Chemistry