ISSN:
1432-2234
Keywords:
Triplet instability
;
Radical character
;
Spin projected UMP
;
Reaction mechanism
;
Transition structures
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The triplet-instability analysis of the closed-shell RHF solutions has been carried out in relation to the orbital and spin correlation effects for various transition structures (TS) and reaction intermediates. It is found that the RHF solutions even for cyclic transition states of the Woodward-Hoffmann symmetry-allowed reactions often involve the triplet instability, indicating the crucial role of correlation corrections. The di- and tetra-radical characters for the transition structures are calculated by the projected UHF (PUHF) solutions resulting from the instability. The spin projection is also crucial for the UHF Møller-Plesset (UMP) correlated wavefunctions obtained for the transition structures of 1,3-dipolar, Diels-Alder, ene and related reactions. The relative stability between cyclic and acyclic TS for these reactions is examined at the approximately projected UHF MP2 (APU MP2) level. The former is found to be more favorable than the latter if the correlation correction is taken into account for TS in a well-balanced manner.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00527740
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