Subject: vibration spectra from force-field calculations

From: Robert Fraczkiewicz <[email-masked]>
Date: Wed, 15 Oct 1997 14:38:40 +0059 (CDT)

Dear Marc-Heinrich,

On Wed, 15 Oct 1997, Marc-Heinrich.Prosenc wrote:
> 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 ?
> 

CCL software archives contain free program RAMVIB that can do both calculate
spectra and refine force fields 
(ftp://www.ccl.net/pub/chemistry/software/SGI/ramvib/). Although it works
only with harmonic force fields, the program is pretty flexible in terms of
force constant definitions. Harmonic force constants are second derivatives
of potential energy; you can use your ingenuity to get (at least 
some) molecular mechanics parameters from these values.

Best regards,
Robert Fraczkiewicz

---

From: Tom Sundius U of Helsinki +358 9 1918339 <[email-masked]>
Date: Sat, 18 Oct 1997 16:26:43 +0300

> some) molecular mechanics parameters from these values.

This transformation is possible, but not quite trivial...
(see, for instance, papers by K. Palmo and S. Krimm (University of Michigan))

+-----------------------------------------------------------------------+
!  Tom Sundius, Dept. of Physics   Internet: [email-masked]    !  
!  University of Helsinki, Finland          [email-masked]    !
+-----------------------------------------------------------------------+