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Re: [ESPResSo] a specific interaction rule between particles

From: Torsten Stuehn
Subject: Re: [ESPResSo] a specific interaction rule between particles
Date: Tue, 17 Aug 2010 11:47:39 +0200
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Dear Narges,

you could also have a look at the implementation of the angledist potiential
which you can find in angledist.h (this potential is not very well tested 
This potential is a "three body + 1 constraint" potential. It calculates a
standard angular potential between 3 particles and additionally varies the
bond angle parameters depending on the distance of the particles to a 
constraint wall.

Best regards,

On 08/17/2010 11:17 AM, Axel Arnold wrote:
> 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

Dr. Torsten Stühn
MPI für Polymerforschung
Ackermannweg 10
55128 Mainz / Germany

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