[gmx-users] Minimisation

Pandya, Akash akash.pandya.15 at ucl.ac.uk
Mon May 22 12:47:53 CEST 2017

Hi all,

During Minimisation I get the following output that the simulation ended prematurely.

Steepest Descents:
   Tolerance (Fmax)   =  1.00000e+03
   Number of steps    =       500000
Step=    0, Dmax= 1.0e-02 nm, Epot=  7.39413e+26 Fmax=         inf, atom= 6640
Step=   14, Dmax= 1.2e-06 nm, Epot=  7.39413e+26 Fmax=         inf, atom= 6640

Energy minimization has stopped, but the forces have not converged to the
requested precision Fmax < 1000 (which may not be possible for your system).
It stopped because the algorithm tried to make a new step whose size was too
small, or there was no change in the energy since last step. Either way, we
regard the minimization as converged to within the available machine
precision, given your starting configuration and EM parameters.

Double precision normally gives you higher accuracy, but this is often not
needed for preparing to run molecular dynamics.
You might need to increase your constraint accuracy, or turn
off constraints altogether (set constraints = none in mdp file)

How do I increase my constraint accuracy? Which file do I have to change?

Best wishes,


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