Charge equilibration

Hi LAMMPS users,

I have a question about using charge equilibration.

According to this message, it seems that it is possible to use Rappé’s charge equilibration method with any force field:

The force-field I am trying to use is the OPLS-AA force field, so I have:

pair_style lj/cut/coul/cut 12.0 15.0

pair_coeff 1 1 0.0556 3.40 # C C

along with bond, bending, and torsion parameters.

And, following the example on

fix 2 all qeq/reax 1 0.0 10.0 1.0e-6 param.qeq

My param.qeq file contains

1 5.343 10.126 0.8563
2 5.343 10.126 0.8563
3 3.006 4.772 0.4174

However, upon running, I get the error message:

ERROR: Must use pair_style reax/c with fix qeq/reax (…/fix_qeq_reax.cpp:322)

I thought this was necessary only if the fix used reax/c as the last parameter instead of a filename?

LAMMPS is compiled with package USER-REAXC. I have tried to unsuccessfully figure out what is causing this error message. I can provide a minimal working example if necessary.

Thank you for the help!

I generally advice against that, because OPLS-AA is fitted with its
pre-defined charges and if charges are changed then you are not using
OPLS-AA anymore. But if you insist, the attached file will work.


fix_qeq_reax.cpp (23 KB)