How to avoid the overlap in Gay-Berne potential ellipsoidal?

When I simulate 2D ellipsoidal in LAMMPS, the particles usually appear to overlap just like in the figure.

and the distribution function also show the overlap,

捕获2

I try to change different parameters in gay-berne potential, but failed.

So, I wonder there is any tips when we apply gay-berne potential to avoid the overlap.

Thanks a lot!

The code I use is:

units	     lj
atom_style   ellipsoid
dimension    2
boundary p p p #periodic boundary cond. in each direction

region	     box block 0 40 0 40 -0.65 0.65
lattice sq 0.18
create_box   1 box
create_atoms 1 box

set 	     type 1 mass 1.0
set 	     type 1 shape 3.0 1.0 1.0

compute	     rot all temp/asphere
velocity     all create 0.8 87287 loop geom
pair_style   gayberne 1.0 1.0 1.0 6.0
pair_coeff   1 1 1.0 1.0 1.0 1.0 1.0 0 0 0

neighbor     0.8 bin

thermo_style custom step c_rot epair etotal press vol
thermo	     100
minimize	0.0 20 10000 10000
reset_timestep 0

timestep     0.002

fix 1 all nve/asphere
fix 2 all langevin 0.2 0.2 2.0 48279 angmom 0.0
fix	     3 all enforce2d

run	     100000

reset_timestep 0

compute	     w all property/atom quatw quati quatj quatk

dump	     * all custom 400 data*.dat &
	     id type x y z c_w[1] c_w[2] c_w[3] c_w[4]

dump	     3 all movie 400 movie.mpg type type &
	     zoom 1.6 center d 0.5 0.5 0.5

run	     40000

The behaviour you observe is normal. If you want to increase the hardness of the potential, you need to increase the energy well depth, or play with the other parameters. Try visualising the shape of the potential for your choice of parameters and you will see that the potential becomes repulsive at contact distances smaller than the ellipsoids’ sigmas.