Hello,

i'm very new here and i hope i'm doing it right.

I'm using Lammps to simulate SAM's on a gold surface. Now i wanted to

test different values for the Lennard Jones and Buck potentials. I

initialized them like this:

-> pair_style hybrid buck 10.0 lj/charmm/coul/long 10.0 12.0

then i parametrized the potentials

-> pair_coeff 1 1 lj/charmm/coul/long 0.255025 3.55768994557802

My question is: can i change the parameters of the LJ potential during

a simulation?

- I tried to use "pair_coeff" again, but when the simulation comes to

that point i get the error below:

-> ERROR on proc 1: Out of range atoms - cannot compute PPPM (pppm.cpp:1512)

Is it possible to change the values of the potential during a simulation?

i hope my question isn't too stupid.

Manuel

Hello,

i'm very new here and i hope i'm doing it right.

I'm using Lammps to simulate SAM's on a gold surface. Now i wanted to

test different values for the Lennard Jones and Buck potentials. I

initialized them like this:

-> pair_style hybrid buck 10.0 lj/charmm/coul/long 10.0 12.0

then i parametrized the potentials

-> pair_coeff 1 1 lj/charmm/coul/long 0.255025 3.55768994557802

My question is: can i change the parameters of the LJ potential during

a simulation?

- I tried to use "pair_coeff" again, but when the simulation comes to

that point i get the error below:

-> ERROR on proc 1: Out of range atoms - cannot compute PPPM (pppm.cpp:1512)

Is it possible to change the values of the potential during a simulation?

yes. it is possible. parameters can be changes between run/minimize

statements at any time.

however, the error indicates that your choice of parameters

may have lead to a numerical instability or very large forces.

any changes made during a run have to be fairly small,

or else the numerical integration of the equation of motions

will not work. an efficient implementation like lammps always

assumes that you are close to equilibrium and thus avoids

all checks and tests for divergence, that would slow down

a well behaved simulations massively.

i hope my question isn't too stupid.

actually, it is much quite on topic for this list.

axel.