How can I get a non-neutral charge with qeq/reax

I am not familiar with the reax/c implementation. As far as I know, it is based on cg solver. So, the constraint on the charge is a lagrangian multiplier. If I changed it to some value other than 0, I think it will work.

However, I am not sure about if change this constraint will generate some extra force that may not included in the formula.