[gmx-users] Problem in energy minimization for a empty membrane system

Bing Bing jarbing09 at gmail.com
Thu Jun 25 11:09:36 CEST 2009

Hi! Thanks a alot for all the suggestions i've got from Justin and Mark.
I found out that i actually deleted the box information from the starting
structure PDB. Once i put it back, It worked. However,
it stopped with this message.

Stepsize too small, or no change in energy.
Converged to machine precision,
but not to the requested precision Fmax < 1000
You might need to increase your constraint accuracy, or turn
off constraints alltogether (set constraints = none in mdp file)

writing lowest energy coordinates.

Back Off! I just backed up em.trr to ./#em.trr.19#

Back Off! I just backed up em.gro to ./#em.gro.11#

Steepest Descents converged to machine precision in 76 steps,
but did not reach the requested Fmax < 1000.
Potential Energy  = -2.24796600790506e+05
Maximum force     =  1.14539522791599e+03 on atom 6619
Norm of force     =  1.62353061702859e+04

Is it mean that the minimization is done and is already converged?
Here the result for the final Step 75.

Energies (kJ/mol)
           Bond          Angle    Proper Dih. Ryckaert-Bell.  Improper Dih.
    1.23491e+03    9.85552e+03    4.48086e+03    4.81663e+03    1.33894e+03
          LJ-14     Coulomb-14        LJ (SR)   Coulomb (SR)   Coul. recip.
    4.09985e+03    8.28955e+03   -1.68827e+04   -1.04035e+05   -1.38691e+05
 Position Rest.      Potential    Kinetic En.   Total Energy    Temperature
    6.95754e+02   -2.24797e+05    0.00000e+00   -2.24797e+05    0.00000e+00
 Pressure (bar)

The position restraint is working fine as well....

Thank you so much.

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