proper forcefield for C60 fullerene

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?

I would appreciate your kind help
thanks

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.