fix qeq/reax on a group of atoms

Dear Lammps users

I read the manual of the fix qeq/reax command. The examples all used “all” as group ID, meanwhile it is said “QEq method minimizes the electrostatic energy of the system by adjusting the partial charge on individual atoms based on interactions with their neighbors”. Does it mean that the charge on all atoms have to be equilibriumed during simulation and it can not apply to a group of atoms in the system?



It is generally a good idea to apply ReaxFF (and thus charge equilibration) to the whole system to get consistent results.
However, if fix qeq/reax is applied to a group different from “all” it will update the charges only for atoms in that group.
It will still consider the interactions of those charges with the charges on all atoms and thus try to minimize the total electrostatic energy.