[gmx-users] angle force constant in mdp file?

[Anton Feenstra]

David wrote:

> On Mon, 2005-06-13 at 12:08 -0700, David Mobley wrote:
> 
>>Dear Gromacs users and team,
>>
>>Concerning restraints, does anyone know why there isn't an option in
>>the mdp files currently for changing angle restraint force constants?
>>For example, dihre-fc and disre_fc are valid options and change the
>>multiplier of the force constant specified in the topology file, but
>>there doesn't seem to be a corresponding parameter for the angle force
>>constant.
>>
>>Does such a parameter exist? If not, does anyone know why not and if
>>this would be expected in the future?
> 
> 
> It does not. Don't know why. Science isn't always rational.
> Anyway you can probably emulate it's functionality by using in your
> topology
> 
> #define MULTFACTOR 1000.0
> #define MYFC(x) (MULTFACCTOR*x)
> 
> And then using rather than your normal force constants
> 
> [ my_function ]
> 1 2 3 4 1 MYFC(3)
> 2 3 4 5 1 MYFC(4)

in addition, you can set MULTFACTOR from the mdp file, with
defines = -DMULTFACTOR=1000.0

-- 
Groetjes,

Anton

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