Dear LAMMPS users,
I’m using ReaxFF for simulating chemical reactions at the interface. My calculation requires non-equilibrium charge state.
One way I thought was to assign a specific value of charge to certain group atoms. To do this, I tried to set a value in the read_data file or use “set” command.
But every case, the charges I set were ignored. I think this is because the reax pair style performs a charge equilibration (QEq) calculation at every time step.
Is there any idea to assign charge value to specific group atoms?
Thanks in advance,
SP
But every case, the charges I set were ignored. I think this is because the
reax pair style performs a charge equilibration (QEq) calculation at every
time step.
that's right - QEq sets the charges - if you want to override that, then
it isn't the ReaxFF force field.
Maybe Aidan can comment on how to go about costraining charge assignment
at a higher level (e.g. by group) and whether it's a good idea (I would
guess no).
Steve
It is certainly possible to formulate a model in this way e.g. charge on
each water molecule constrained to zero. However, the ReaxFF potentials
provided with LAMMPS, and the LAMMPS implementation, do not allow this.
Instead, charge is assumed to move freely between all atoms. It is important
to note that this usually produces reasonable behavior e.g. the charge on
each water molecule fluctuates about zero.