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Structure and stability of [C 2 H 4 N] + singlet‐state cations: Comparison between DFT and high‐level ab initio calculations
Author(s) -
Corral Inés,
Mó Otilia,
Yáñez Manuel
Publication year - 2002
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.10438
Subject(s) - singlet state , ab initio , chemistry , potential energy surface , maxima and minima , ab initio quantum chemistry methods , ethylene , electronic correlation , yield (engineering) , atomic physics , computational chemistry , physics , excited state , molecule , thermodynamics , mathematics , mathematical analysis , biochemistry , organic chemistry , catalysis
The stationary points of the [C 2 H 4 N] + singlet potential energy surface have been characterized by means of B3LYP/6‐311+G(3 df ,2 p ) and G2(MP2) approaches. A comparison between both sets of results shows that, although both methods yield similar values for the relative stability of the local minima, they differ significantly regarding the stability of some transition states, in particular those corresponding to 1,3‐H shift processes. This implies that the dynamics of the corresponding reaction may exhibit substantial differences if based on B3LYP or high‐level ab initio potential surfaces. The attachment of N + to the CC bond of ethylene is preceded by a charge transfer and, as a consequence, a symmetry breaking problem arises. Our results show that inclusion of high‐order correlation contributions through the participation of triple excitations may be crucial. The B3LYP method is not a good alternative to treat this problem due to the spin contamination of the unrestricted treatment. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003