[gmx-users] problems with energy minimization

Martin mstiebri at biologie.uni-erlangen.de
Mon Aug 28 14:21:48 CEST 2006


Dear all,

I´m a beginner in the field of molecular dynamics and have just installed the 
gromacs software.
I have problems with energy minimization. When trying out the md tutorial on 
the lysozyme structure 1AKI.pdb using the provided minim.mdp file the 
minimization finishes with the 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 minim_traj.trr to ./#minim_traj.trr.4#

  Back Off! I just backed up confout.gro to ./#confout.gro.4#

  Steepest Descents converged to machine precision in 79 steps,
  but did not reach the requested Fmax < 1000.
  Potential Energy  = -1.13948846313191e+04
  Maximum force     =  1.94715000386709e+03 on atom 1113
  Norm of force     =  8.53155624640669e+03

I already tried different minimization algorithms with different settings and 
also compiled the code with double precision accuracy without success.

Thank you very much for any advice,
Martin




More information about the gromacs.org_gmx-users mailing list