Thank you very much for your reply, Mark It is the topology problem. It seems I did it in a wrong way. Now the topology goes like this: [ molecules ] ; Compound #mols Protein_chain_A 1 Protein_chain_A2 1 POPC 256 This problem solved.
But then comes a new one. When I did the g_membed, the system blowed up after one iteration! I think I really shouldn't ignore the warning from the grompp. However, as an inexperienced user, I don't know how to improve the mdp file. Can you give me any hint? The mdp file for the g_membed is like this: cpp = /lib/cpp ; Run parameters integrator = md nsteps = 1000 dt = 0.002 ; Output control nstxout = 10 nstvout = 10 nstenergy = 10 nstlog = 10 ; Bond parameters continuation = no constraint_algorithm = lincs constraints = all-bonds lincs_iter = 1 lincs_order = 4 ; Neighborsearching ns_type = grid nstlist = 1 rlist = 1.4 rcoulomb = 1.4 rvdw = 1.4 ; Electrostatics coulombtype = PME pme_order = 4 fourierspacing = 0.16 ; Temperature coupling is on tcoupl = V-rescale tc-grps = Protein Non-Protein tau_t = 0.1 0.1 ref_t = 300 300 ; Pressure coupling is on Pcoupl = Berendsen pcoupltype = semiisotropic tau_p = 1.0 compressibility = 4.5e-5 4.5e-5 ref_p = 1.0 1.0 ; Velocity generation gen_vel = yes gen_temp = 300 gen_seed = 173529 ; Energy monitoring energygrps = Protein ; Non-equilibrium MD freezegrps = Protein freezedim = Y Y Y ; Energy group exclusions energygrp_excl = Protein Protein Thanks a lot! Linda
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