[gmx-users] Three-site model for acetonitrile

Christoph Freudenberger christoph.freudenberger at chemie.uni-ulm.de
Mon Feb 24 15:01:52 CET 2003

David van der Spoel wrote:
> How about energy?  Any idea if the potential energy is OK for your
> system? 
I just compared the the potential energy of the MeCN-System with that
of my other systems:
MeCN: 		-3500 KJ/mol (or whatever comes out of g_energy)
CH2Cl2:		-6000
MeOH:		-13800
DMSO:		-21300
The Systems do contain different numbers of atoms, I don't know if that
makes any diffrence for the values calculated by g_energy.

> How do you keep it linear? You probably want to define a
> topology with a dummy for this..
I do not use any constraints. While double-checking the forcefield
of MeCN i realized, I had set the bond length of the C-N triple bond
to small (0.1nm instead of 0.116nm).

Could that be the reason?
I just started a simulation to find out...

Could a wrong bond/angle force constant result in that kind of behaviour?
Christoph Freudenberger
Abt. Organische Chemie I AK Siehl - Uni Ulm -Tel: ++49-731-502-2785

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