[gmx-users] Stepsize too small, or no change in energy

[Jochen Hub]

Srivastava, Dhiraj (UMC-Student) wrote:

>Hi all
>
>      when i am trying to minimize my structure, i am getting following error.
>
>Stepsize too small, or no change in energy.
>Converged to machine precision,
>but not to the requested precision Fmax < 1000
>  
>
This is not an error. If your Fmax is around 1e+4 and your Epot around 
-1e+6 everything is fine...

Good luck, Jochen

>Double precision normally gives you higher accuracy.
>
>writing lowest energy coordinates.
>
>Back Off! I just backed up prodh_em.trr to ./#prodh_em.trr.2#
>
>Back Off! I just backed up prodh_wb.pdb to ./#prodh_wb.pdb.4#
>
>Steepest Descents converged to machine precision in 45 steps,
>but did not reach the requested Fmax < 1000.
>Potential Energy  = -1.8373166e+06
>Maximum force     =  1.5158329e+04 on atom 519
>Norm of force     =  3.1759754e+04
>
>
>i have tried the conjugated gradient, constraint none and also included flexible water but still i am getting the same error.
>
>what should i do to solve this problem?
>
>Thanks in advance for help.
>
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-- 
************************************************
Jochen Hub
Max Planck Institute for Biophysical Chemistry
Computational biomolecular dynamics group
Am Fassberg 11
D-37077 Goettingen, Germany
Email: jhub[at]gwdg.de
************************************************