Subject: CHARMM reaction coordinate

From: [email-masked] (Peter Varnai)
Date: Tue, 11 Mar 1997 09:30:45 +0000 (GMT)

Dear Charmm-Users,

Could someone help me understand how to define the reaction coordinate
for a qm/mm calculation. 
I would like to step over a few points on a reaction coordinate
and minimize the energy.
My first guess was to use the RESDistance command, but I don't really understand
the RVAL definition from the example given in doc/cons.doc.
Thank you very much for your time.

Regards,

Peter Varnai

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From: A J Turner <[email-masked]>
Date: Tue, 11 Mar 1997 12:37:28 +0000 (GMT)

Hi!

Several methods are availible to you.  The most effective that I have come
into contact with  is to use high force internal coordinate constraints to
hold a coordinate at a desired value.

The snag with this is that it tends to cause convergence problems with the
optimisers, thus if you are only working in one dimension, I would suggest
trying cons-fix for the atoms on either end of a desired bond (if you are
tracing a bond!).

The IC edit command can then be included in a charmm loop to plot out the
coordinate.

Good luck

Alex

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|Alexander J Turner         [email-masked]                  |
|Post Graduate              |http://www.bath.ac.uk/~chpajt/home.html|
|School of Chemistry        |+144 1225 8262826 ext 5137             |
|University of Bath         |                                       |
|Bath, Avon, U.K.           |Field: QM/MM modeling                  |
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