Trimethylenemethane. Comparison of Multiconfiguration Self-Consistent Field and Density Functional Methods for a Non-Kekulé Hydrocarbon

Relative energies for different multiplets of trimethylenemethane and methylenecyclopropane are calculated at MCSCF, CASPT2N, and DFT levels of theory. Comparison to the experimentally measured heat of formation for the 3A2‘ state and to the experimentally measured 3A2‘−A1 gap permits analysis of th...

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Bibliographic Details
Published in:Journal of physical chemistry (1952) 1996-06, Vol.100 (23), p.9664-9670
Main Authors: Cramer, Christopher J, Smith, Bradley A
Format: Article
Language:English
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Summary:Relative energies for different multiplets of trimethylenemethane and methylenecyclopropane are calculated at MCSCF, CASPT2N, and DFT levels of theory. Comparison to the experimentally measured heat of formation for the 3A2‘ state and to the experimentally measured 3A2‘−A1 gap permits analysis of the relative importance of active space and basis set selection in the multiconfigurational methods. Such comparison also reveals that while DFT accurately treats triplet trimethylenemethane, there is a limitation in present DFT functionals with respect to accurately treating nondynamic correlation effects for closed-shell singlets in a molecule characterized by degenerate frontier molecular orbitals. Implications for calculations on larger systems are discussed.
ISSN:0022-3654
1541-5740
DOI:10.1021/jp953697x