Re: [ESPResSo-users] Restricting interactions to nearest neighbors

[Henri Menke]

On 19/09/18 17:00, Memet, Edvin wrote:
> Dear all,
> 
> Could anyone point me in the right direction for how to restrict, say, a 
> LJ interaction to act only between nearest neighbors? I've seen there is 
> an 'exclusion' feature, which allows you to specify a neighborhood in 
> which the interaction doesn't occur, but I see no analogous feature for 
> what I'm looking for. [By the way, I'm (still) using tcl-Espresso ...]

It's not so clear what you are after.  By default, LJ is a short-range
interaction, i.e. it only affects neighbouring particles within r_cut.
Actually r_cut is a mandatory parameter (... are optionals):

inter type1 type2 lennard-jones epsilon sigma r_cut [ ... ]

See also
http://espressomd.org/wordpress/wp-content/uploads/2017/06/ESPResSo_3.3.1_UsersGuide.pdf#subsection.5.1.2

Hence you can set the nearest neighbour distance by r_cut.

> 
> I've also noticed there is a nbhood routine which returns a list of 
> particles inside a certain radius, but unfortunately it does not return 
> an ordered list (sorted by distance). So perhaps, possible helpful 
> answers could indicate how to modify the nbhood routing to return an 
> ordered list, or other ways to access the nearest neighbor in the source 
> code.
> 
> Best,
> Edvin
>