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The N 2 problem in molecular CI calculations
Author(s) -
Meunier A.,
Levy B.,
Berthier G.
Publication year - 1976
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.560100617
Subject(s) - spurious relationship , physics , perturbation theory (quantum mechanics) , molecule , hydrogen molecule , perturbation (astronomy) , benzene , electron , square (algebra) , scheme (mathematics) , atomic physics , quantum mechanics , statistical physics , chemistry , computational chemistry , mathematics , mathematical analysis , statistics , geometry , organic chemistry
The possible existence of spurious terms increasing as the square of the number of electrons is theoretically proved for the CI treatments of molecules limited to single and double excitations, and is revealed by some numerical calculations (alcanes and juxtaposed hydrogen molecules). An improved perturbation scheme is suggested in order to evaluate the CI energy lowering more carefully. Covergence difficulties are found for larger systems (benzene).