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A scaled force field for polyenes derived from ab initio calculations including electron correlation effects
Author(s) -
Kofranek M.,
Karpeen A.,
Lischka H.
Publication year - 1990
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.560382472
Subject(s) - anharmonicity , force field (fiction) , chemistry , electronic correlation , ab initio , scaling , computational chemistry , diagonal , force constant , harmonic , molecular physics , atomic physics , physics , molecule , quantum mechanics , mathematics , geometry , organic chemistry
Abstract Geometries and harmonic force constants were calculated for trans ‐ and gauche ‐butadiene and for trans ‐ hexatriene using SCF and electron correlation ( ACPF ) methods. By comparing the results of these two procedures trends in the errors of the SCF values are discussed. Although diagonal SCF force constants are usually too large in relation to correlated results, the opposite is true (in absolute value) for several off‐diagonal force constants referring to the carbon backbone. Scaling techniques are used in order to correct for these deficiencies and also for anharmonicity effects. On that basis scaled SCF force fields and vibrational frequencies were calculated for trans ‐polyenes up to 14 carbon atoms and for the infinite chain.