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Re: [lammps-users] proper forcefield for C60 fullerene
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Re: [lammps-users] proper forcefield for C60 fullerene


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Mon, 31 Jul 2017 18:52:28 -0400



On Mon, Jul 31, 2017 at 4:42 PM, Ali Shomali <ali.shomali111@...24...> wrote:
Hello Dear LAMMPS users

I'm trying to simulate shock wave production in  C60 fullerene crystals structures.
the problem is that since Rebo potential doesn't have long range terms, my structures compress so easily because c60 molecules don't interact so I use Airebo potential with lj term on to compensate the differences but this term makes the solid so hard to compress at high pressures and density change becomes abnormal.therefore I should apply a very great pressure to see the phase transition.  some papers also include an additional core-core Vdw force to get more accurate results how ever I cant use this method either cause in my shock modeling C60 molecules deform and 'core' cannot be defined any more. so is there any way to reduce the VdW when molecules start to get too close? or to avoid this problem by changing long range interaction form? 

​please note, that this is not really a LAMMPS questions, but a force field question, so your chances to find helpful answers are the best by continuing searching and reviewing the published literature. as for "softening" the repulsive part of AIREBO, have you looked at AIREBO-M, i.e. pair style airebo/morse, which uses a morse function as repulsive part instead of a (stiffer) 12-6 lennard-jones. i strongly recommend to study the associated publication, though. what you are asking for is quite a lot for a classical potential to provide.

axel.


 
I would appreciate your kind help
thanks 



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--
Dr. Axel Kohlmeyer  akohlmey@...12...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.