[gmx-users] frezzing a bond

Elton Carvalho eltonfc at if.usp.br
Tue Jul 20 16:34:27 CEST 2010

Justin A. Lemkul wrote:
> Nilesh Dhumal wrote:
>> How can I freeze a bond?
> How about distance restraints instead?

That raises some kind of off-topic question: In Cerius2, we use
position constraints to reduce the calculation complexity, because
forces between constrained atoms need not to be evaluated, this saves
some simulation time. And, in our group, that's practically the only
reason to do so.

Now, if I recall corectly, postion and distance restraints are like
stiff springs keeping the atom in a certain distance/position. Does
this take more, less or the same computation time as if the bonds were

Is it possible to use constraints in gromacs as I mentioned above?

Elton Carvalho
Tel.: +55 11 3091-6985/6922
Dept Física dos Materiais e Mecânica
Instituto de Física
Universidade de São Paulo
P.O. Box 66318 - 05314-970 São Paulo-SP, Brazil

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