Subject: Re: CCL:calculated IR frequencies

From: elewars <[email-masked]>
Date: Tue, 17 Dec 2002 10:42:38 -0500

2002 Dec 17

Re calc and exp IR freqs, harmonic corrections and exp corrections:

Harmonic freqs:
K. P. Huber, G. Herzberg, "Molecular Spectra and Molecular Structure. IV. Constants of Diatomic Molecules", Van Nostrand Reinhold, New York, 1979.

Calc freqs cf. raw exp. and harmonic:
W. J. Hehre, L. Radom, P. v. R. Schleyer, J. A. Pople, "Ab Initio Molecular Orbital Theory", Wiley, New Yprk, 1986, pp 234-5.
A. St-Amant, chapter 2, p 235, in "Reviews in Computational Chemistry, Vol. 7, K. B. Lipkowitz and D. B. Boys, Eds., VCH, New York, 1996.
F. Jensen, "Introduction to Computational Chemistry", Wiley, New York, 1999, pp 271-4.

Empirical correction of calc freqs to agree better with exp (probably the canonical paper):
A. P. Scott, L. Radom, J. Phys. Chem., 1996, 100, 16502.

E. Lewars
============

pop14848 wrote:

> Hi,
>
> can someone point me to a paper discussing calculated IR frequencies vs. experimental frequencies? I am not intersted in differences between DFT and HF/MP2 calculations but the general reasons of the overestimated IR-frequencies due to harmonic fundamentals instead of anharmonicity aswell as too short bond-length (in HF calcilations) etc.
> In fact a paper not only disussion a mediate factor of about 0.9 but also discussing the difference of this factor from calculated frequence to frequence in one molecule would be perfekt (like 0.90 for one one normal mode, 0.93 for the next)
>
> Thanks in advance
>
> Eike Huebner
>
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