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Basis set effects and the choice of reference geometry in ab initio calculations of vibrational spectra
Author(s) -
Michalska D.,
Schaad L. J.,
C̆arsky P.,
Andes Hess B.,
Ewig C. S.
Publication year - 1988
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540090508
Subject(s) - bond length , ab initio , basis (linear algebra) , basis set , molecular geometry , superposition principle , magnitude (astronomy) , energy minimization , chemistry , geometry , spectral line , computational chemistry , gaussian orbital , molecular physics , ab initio quantum chemistry methods , atomic physics , physics , mathematics , molecule , quantum mechanics , density functional theory , astronomy
Tatewaki and Huzinaga's [J. Comput. Chem. 1 , 205 (1980)] basis sets, constructed to minimize superposition error, were used to calculate infrared (IR) frequencies and intensities. They were found inferior to Pople bases such as 3–21G and 6–31G*. The question of whether a theoretical vibrational spectrum should be computed at experimental or theoretical bond lengths was also investigated. If the magnitude of the correlation energy increases with bond length, Hartree‐Fock bond lengths are expected to be shorter than experimental, and frequencies computed there will be higher than those computed at experimental lengths. Conversely, if this magnitude decreases with R , computed lengths should be longer than experimental and should give lower computed frequencies.