BENZENE FORCE CONSTANTS
References on "Force constants of Benzene"
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In addition to the references already cited:
-P. Pulay, G. Fogarasi, J.E. Boggs, J. Chem. Phys., 74 (1981) 3999
-H. Guo and M. Karplus, J. Chem. Phys.,89(1988) 4235
There is one additional important reference for Benzene:
-A.G. Ozkabak, L. Goodman, J. Chem. Phys.,87(1987) 2564
The latter can be considered as an "experimental force field"; the
authors
have submitted recently a review paper, comparing this FF to high level
ab initio calculations:
-L. Goodman, A.G. Ozkaback and S.N. Thakur, "A Benchmark Vibrational
Potential Surface: Ground State Benzene", J. Phys. Chem. , accepted.
Finally, as pointed out by A. Holder in a previous E-mail, there are no
scale factors available in the litterature for these type of compounds and
adapted to Hessians calculated at the semi-empirical level such as AM1 and MNDO.
We have recently submitted a paper on the subject:
-N. Rougeau, J.P. Flament, P. Youkharibache; H. P. Gervais, G. Berthier
"Vibrational Modelling in large Polycyclic Aromatic Hydrocarbons"
J. Mol. Struct. (Theochem), accepted for publication.
describing a Scaled Force Field for Benzene and larger polycyclic aromatic
hydrocarbons (PAH) of astrophysical interest: calculating the Hessian at the
MNDO level, determining scale factors independently for benzene and naphtalene
to test their transferability, and using this set of transferable scale factors
to calculate a scaled Hessian and associated vibrational frequencies.
The overall agreement between experimental and MNDO-SQM frequencies for
all molecules in the series (benzene, naphtalene, anthracene, phenanthrene,
pyrene and coronene) is around 25-30 cm-1.
Philippe Youkharibache
internet: youkha[ AT ]biosym.com
tel: 619-546-5562