Hi Xiaobing,
I am not sure though, are you trying to put hybrid style (Tersoff and PPPM) for the same set of atoms? Since both are pair_sytle commands, I think it is not permissible and that is the reason it is crashing.
You cant have two pair styles for same set of pair interactions
If somehow, you can alter the code and treat Tersoff as bond_style type of potential, then you can define bond_style Tersoff and pair_style PPPM/etc…