Charged sphere macromolecule and problem in definition its charge

Hi dear LAMMPS users

I am simulating a charged macromolecule as a large sphere particle, but regardless of the particles diameter, the maximum charge that I can define is 16e.

If I define the charge of particle more than 16 my initial pressure increases and the error “out of range atoms-cannot compute PPPM” occures. so what is your idea about this problem?

I consider other particles as point particles and try both of sphere and point particle (sigma=20 Angstrom) for macromolecule

Thanks for your advice

Best regards

Majid

Thtat's not a LAMMPS limitation. The error is b/c you're
generating bad dynamics with a heavily charged particle.
So some particle is moving too far within a timestep
and before reneighboring. See the Error section
of the manual for suggestions on how to adjust for it.

Steve

Thtat's not a LAMMPS limitation. The error is b/c you're
generating bad dynamics with a heavily charged particle.
So some particle is moving too far within a timestep
and before reneighboring. See the Error section

actually, in this case it is more likely that the
forces are overflowing into a NaN or Inf which
will cause the same error message.

of the manual for suggestions on how to adjust for it.

regardless, it is impossible to give detailed advice
without an example input being made available.

axel.

Dear Steve & Axel

Thanks for your answers

The problem is here that other particles do not respect the large particle’s diameter and they pass it’s boundary and move inside the particle, so it causes a bad overlapping in the system. This is done while my initial coordinates shows no overlapping. I use sphere atom style and lennard jones potential with diameter=Sigma=20.0 Angstrom and there is no atom in the distance of 22 Angstrom from the large particle’s center in my initial coordinates.

Is it because of my neighbor skin which is 2.0 Angstrom? I increase it till 20 Angstrom, but it can not remove the problem. ( I use neigh_modify delay 0 every 1 check yes)

What is your idea about my problem?

Thanks alot

Majid

Dear Steve & Axel

Thanks for your answers

The problem is here that other particles do not respect the large particle's
diameter and they pass it's boundary and move inside the particle, so it
causes a bad overlapping in the system. This is done while my initial
coordinates shows no overlapping. I use sphere atom style and lennard jones
potential with diameter=Sigma=20.0 Angstrom and there is no atom in the
distance of 22 Angstrom from the large particle's center in my initial
coordinates.

Is it because of my neighbor skin which is 2.0 Angstrom? I increase it till
20 Angstrom, but it can not remove the problem. ( I use neigh_modify delay 0
every 1 check yes)

What is your idea about my problem?

it is pointless to speculate without having proper information.
all i can say is "you must be doing something wrong".

unless you post a *complete* example input that people can
look at and properly debug and dissect, you will have to
either help yourself or pick a different project.

axel.