[lammps-users] proteins as a rigid bodies

Hi, i’am new in lammps. i try to simulate 2 proteins as a rigid bodies(each of them has a layer of water 3A, total numbers of atoms almost 8000) in order to approach each other. i used fix_rigid command for proteins but simulation runs too slowly(like an all atom figuration)almost 10 steps per 25sec. could you sent me an appropriate input script about that. thanks in advance.