Re: [ESPResSo-users] VIRTUAL_SITES

[Rudolf Weeber]

Hi,

On Mon, Sep 08, 2014 at 02:57:56PM +0200, Dudo wrote:
> please is it possible to set a virtual particle in the center-of-mass of
> each two consecutive real particles in a polymer chain?
> Am I right that in such the case a given virtual site would need to be part
> of two molecules?
> Do the sites stay in the COM, or are their positions being updated within
> the simulation?
I don't think, this is possible with the current implementation of 
VIRTUAL_SITES_COM, because the molecule id (mol_id particle property) needs to 
be set on all constituents of the object, for which a virtual site is to be 
set, and you can have only one mol_id per particle.

I do not believe that this is a fundamental problem, though. It would be 
possible to write an implementation of virtual sites at the center of mass 
without this restriction, e.g., by using bonds to describe the relationship 
between virtual and non-virtual particles.
The difficulty of implementing this would probably be on the medium level.

Regards, Rudolf