Gamma parameter in fix qeq/reax

Dear lammps users and Ray Shan,

I am trying to use QEq to calculate charges of atoms. When the Taper upper radius is 10 A the charges are meaningless (I mean they are so high, +3, -5, etc). When I decrease its value the charges are better.

I also tried to reproduce the QEq charges of some molecules (H2O, CH4, HF) reported in the original paper of QEq (The Journal of Physical Chemistry 95 (1991) 3358-3363) and I got the similar results when the upper Taper radius is around 2 A.

I did all simulations with k-space switched off.

What should the upper Taper radius value be?