Subject: Re: CCL:normal mode force constant

From: "Robert Fraczkiewicz" <[email-masked]>
Date: Mon, 1 Dec 1997 10:51:43 -0600

Frederique,

> I would like to get the normal mode force constant for each bond of a
molecule
> to use them in the equation of Marcus theory. I do not know how to calculate
> the normal mode force constant for a bond. I would be pleased if somebody
> could help me to solve this problem.
>
> Thank you.
>
> Frederique

I assume that you are interested in a harmonic force field. Normally, you need
to do elaborate ab initio calculations to get good force constants. But if you
have a good set of experimental data (IR, Raman; the more isotopomers, the
better), then you can use RAMVIB to quickly fit force constants to observed
vibrational frequencies. Usually, the quality of fit will be much better than
that from ab initio. However, assignments and force constant selection will be
the hard part. RAMVIB has some auxilliary programs to make it easier. It is
available free of charge to academic users at CCL archives:

ftp://www.ccl.net/pub/chemistry/software/SGI/ramvib/

Best regards,
Robert Fraczkiewicz

University of Texas Medical Branch
Galveston, TX 77555