Subject: Re: CCL:vibration spectras from force-field calculations

From: Per-Ola Norrby <[email-masked]>
Date: Thu, 16 Oct 1997 12:30:11 +0200

Dear Marc,

>it would be kind if anyone could tell me if there exist a program that
>calculates
>vibrational spectras from forcefields like MM2 or DISCOVER or HYPERCHEM
>.... for free ?
>
>do there any public domain routines exist, which are able to refine
>existing forcefields
>like mm2 or amber when the IR-spectrum is given ?

	You should look up Tinker, from Jay Ponders lab.  Check it out at:

http://dasher.wustl.edu/tinker

	It's pretty hard to use IR spectra in the parameterization, and
anyway, MM2 and AMBER aren't built to reproduce IR spectra.  A few
molecular mechanics force fields are, for example MM3 (available in Tinker)
and CFF.  In any case, I recommend parameterizing from a quantum chemical
Hessian directly, not from the actual spectrum (a bit hard to do if what
you have is the experimental spectrum :-).  In most cases, it's almost
hopeless to match normal modes between calculated and experimental
spectrum, whereas the Hessian elements are well defined.  Look up the work
of Lifson & Warshel (CFF), Rasmussen (CFF-Lyngby), Hagler (CFF9x), Halgren
(MMFF), ...

	Best Regards,

	Per-Ola Norrby

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 *  Per-Ola Norrby, Associate Professor
 *  The Royal Danish School of Pharmacy, Dept. of Med. Chem.
 *  Universitetsparken 2, DK 2100 Copenhagen, Denmark
 *  tel. +45-35376777-506, +45-35370850    fax +45-35372209
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