[gmx-users] Turn off the diheral energy

[Tsjerk Wassenaar]

Hi Myunggi Yi,

>
> Mixing force fields is an intrinsically bad idea. See
> http://wiki.gromacs.org/index.php/Parameterization
>

I second that...

> > Is it possible to turn off dihedral energy (proper and improper) for a
> > certain molecule?
> > If yes, then how can I do this?
>
> Comment out these parts of your topology file.
>

You can do this easily by enclosing the dihedral section with an
#ifdef ... #endif block, and use a control #define statement upstream
of it:

#define INCLUDE_DIHEDRALS

#ifdef INCLUDE_DIHEDRALS
[ dihedrals ]
...
...
...
#endif

This even allows you to control it through the .mdp file, including the line

define = -DINCLUDE_DIHEDRALS

Hope it helps,

Tsjerk

-- 
Tsjerk A. Wassenaar, Ph.D.
Junior UD (post-doc)
Biomolecular NMR, Bijvoet Center
Utrecht University
Padualaan 8
3584 CH Utrecht
The Netherlands
P: +31-30-2539931
F: +31-30-2537623