Dear Dongsheng,
There is a difference between “pair_style lj/class2 and pair_style coul/debye” and what you asked in your first mail. “pair_style hybrid lj/class2/coul/debye 0.01 2.5 25.0 lj/cut/coul/debye 0.01 2.5 25.0”
What you probably want is
“pair_style hybrid lj/class2 10.0 lj/cut/coul/debye 0.01 2.5 25.0”
Regards,
Vikas