my em.mdp file is as follows: integrator = steep nsteps = 50000 nstcomm = 1 emtol = 10 emstep = 0.01 ns_type = grid rlist = 0.8 coulombtype = cut-off vdwtype = Cut-off rcoulomb = 0.8 rvdw = 0.8 tcoupl = no pcoupl = no gen_vel = no constraints = none periodic_molecules = yes