[MMTK] 3 body force field and electric field

[hinsen at cnrs-orleans.fr]

On 05.06.2004, at 00:01, Tandia, Adama wrote:

> Is some sort of 3 body force field like Axilrod-Teller or Stillinger  
> weber developed in MMTK;

No. The only three-body term implemented is the bond angle term.

> If not, has anybody ever tried to implement it?

I didn't, but I don't expect any difficulty. Any force field term that  
is a function of the coordinates can be implemented as demonstrated in  
the example code for a harmonic interaction term.

> Second question: Is it possible to apply electric field on a structure  
> during a regular MD run?
>
Yes, but it takes more effort than just specifying an option. You need  
to write a force field term that calculates the forces and energy due  
to the electric field. Then you add it to the standard (Amber force  
field), i.e.:

	universe.setForceField(Amber94ForceField() +
		ElectricField(universe, 2.*Units.V/Units.m)

That's it. Every energy-related routine will automatically take the  
field into account.

Actually, the electric field is so simple to do that I might write it  
as an additional example code. But not today...

Konrad.
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Konrad Hinsen
Laboratoire Leon Brillouin, CEA Saclay,
91191 Gif-sur-Yvette Cedex, France
Tel.: +33-1 69 08 79 25
Fax: +33-1 69 08 82 61
E-Mail: hinsen at llb.saclay.cea.fr
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