Re: [ESPResSo] a specific interaction rule between particles

[Axel Arnold]

On Tuesday 17 August 2010 09:54:01 address@hidden wrote:
> Dear all,
> I have a problem in which some particles have a
> specific interaction rule. Their interaction energy depends on their
> distance from each other as well as their distance from a surface. So the
> interaction of two particles depends on three parameters: particles
> distance from each other
> and distance of each of them from the
> surface.  Particle-particle and particle-surface interactions are both
> short-range. Is there any way to handle these interactions with Espresso,
> even by some changes in the source files? for eg. is it possible to change
> the tabulated interaction to depend on 3 parameters? Some general guides
> are also very useful!

Hi!

I guess that since you have 3 parameters, it will be rather difficult to 
tabulate the interaction, so there should be some analytic description. In 
this case, the easiest thing is to look at for example the smooth step 
potential, which you can find rather easily by using grep for SMOOTH_STEP and 
looking at steppot.h. You basically need to write a new header file for your 
interaction, and write corresponding code to each of the SMOOTH_STEP #ifdefs.


The pair force functions also obtain pointers to both particles, so you can 
simply look at the particle positions, and do what ever you like with them, 
for example adapting your potential.

Many regards,
Axel

-- 
JP Dr. Axel Arnold Tel: +49 711 685 67609
ICP, Universität Stuttgart      Email: address@hidden
Pfaffenwaldring 27
70569 Stuttgart, Germany