Re: [ESPResSo-users] Fix the orientation of a Rod

[Olaf Lenz]

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Hi Salvador!

Sorry for the late reply, but we had some work to resolve your question.

On 02/20/2013 03:38 PM, Salvador H-V wrote:
> I have created an initial lattice configuration with all the rods 
> oriented in z-direction.
> 
> I was wondering if somebody could give me a hint of how to
> randomize the position of the rods but keeping the orientation. So,
> what I need is the rods in random positions but all of them with
> director vector parallel to axis z.

Indeed, the fix command will only fix the translational degrees of
freedom.

However, we do have a solution. Since some days, we have the feature
"ROTATION_PER_PARTICLE", which allows to turn the rotational degrees of
freedom on and off on a per-particle basis. When you turn off the
rotation of a particle ("part $pid rotation 0"), the particle will not
rotate anymore, even though it still has an orientation.

We had this feature lying around since quite a while, but we were not
sure how to include it into ES. Caused by your request, we (i.e.
Rudolf!) have resolved the issues and introduced the new feature.

Note that the feature is not in the latest release yet, but so far only
lives in the development code of ESPResSo. It will be included in
ESPResSo 3.2 which is expected to be released in April.

Olaf
- -- 
Dr. rer. nat. Olaf Lenz
Institut für Computerphysik, Allmandring 3, D-70569 Stuttgart
Phone: +49-711-685-63607
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