Subject: summary normal mode force constant

From: <[email-masked]>
Date: Tue, 16 Dec 1997 11:13:13 +0100 (NFT)

Dear CCL,

I would like to thank all the people who answered my question about normal 
mode force constant. You can find below my questions and the answers I 
received.

Frederique

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Dear CCL,

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

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Frederique BARBOSA				Institute for Organic Chemistry
						University of Basel
E-mail : [email-masked]		St. Johanns-Ring 19
phone  : 061/267 11 57				4056 Basel
fax    : 061/267 11 05				Switzerland
================================================================================

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>From [email-masked] Thu Nov 27 15:38:17 1997

Dear Frederique,

As far as I can understand you need force constants in internal coordinates.
There is a good article, that describes all mathematical details of such a
conversion:
J.A.Boatz and M.S.Gordon, J.Phys.Chem. 93, 1819-1826(1989).
This algorithm is implemented in GAMESS, so you can use it for your
practical needs.

Yours,
Victor.

   ***     Institute of Chemical Physics in Chernogolovka     ***
   *                Russian Academy of Sciences                 *
   *                  Dr. Victor M. Anisimov                    *
   *  Pervaya-21, Chernogolovka, Moscow region, 142432, Russia  *
   *         FAX: +7 (096) 576-4009,  +7 (096) 515-3588         *
   ***               E-mail: [email-masked]                ***

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>From [email-masked] Thu Nov 27 19:31:04 1997

Hi Frederique,

There is an old paper of Walter Gordy:

A relation between bond force constants, bond orders, bond lengths, and the
electronegativities of the bonded atoms.  J. Chem. Phys. 14:305 (1946)

Wish it is helpful.

Regards,

Shan-Li Wang

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>From [email-masked] Mon Dec  1 17:42:46 1997

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

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================================================================================
Frederique BARBOSA				Institute for Organic Chemistry
						University of Basel
E-mail : [email-masked]		St. Johanns-Ring 19
phone  : 061/267 11 57				4056 Basel
fax    : 061/267 11 05				Switzerland
================================================================================