# Energy Minimisation error

**URL:** <https://gromacs.bioexcel.eu/t/energy-minimisation-error/5744>\
**Category:** User discussions\
**Tags:** mdp-parameters, mdrun, energy-minization\
**Created:** [February 7, 2023, 9:53am UTC](https://gromacs.bioexcel.eu/t/energy-minimisation-error/5744 "2023-02-07T09:53:38Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![BinodLK](https://avatars.discourse-cdn.com/v4/letter/b/c4cdca/32.png) [@BinodLK](https://gromacs.bioexcel.eu/u/BinodLK)\
**Post date:** [February 7, 2023, 9:53am UTC](https://gromacs.bioexcel.eu/t/energy-minimisation-error/5744/1 "2023-02-07T09:53:38Z")

</div>

GROMACS version: version 2020.1-Ubuntu-2020.1-1  
GROMACS modification: No

Hello Everyone,  
I’m trying to do energy minimisation for my system which contains a protein (441 residues), 25 Cu2+ ions, 52 Cl- ions and 10 molecules (phenylindane). solvent is water.

I’m getting the error of,  
Energy minimization has stopped, but the forces have not converged to the  
requested precision Fmax \< 10 (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)

writing lowest energy coordinates.

Steepest Descents converged to machine precision in 78 steps,  
but did not reach the requested Fmax \< 10.  
Potential Energy = 4.4149275e+06  
Maximum force = 2.2788421e+08 on atom 2405  
Norm of force = 4.2649535e+05

I have read previous solutions for this error and did everything as they suggested in here,

> [@Energy minimization error](https://gromacs.bioexcel.eu/t/energy-minimization-error/478):
>
> GROMACS version: 2020-3 GROMACS modification: No Dear all, Hello, my name is Tiara. I am new to Gromacs and molecular dynamic. I am trying to do a simulation to a protein complexed with ligand. When I tried to minimizing energy [gmx mdrun -v -deffnm EM -nt 1], I got this following error: Steepest Descents: Tolerance (Fmax) = 1.00000e+01 Number of steps = 50000 Step= 0, Dmax= 1.0e-02 nm, Epot= -6.34945e+05 Fmax= 1.91991e+05, atom= 2089 Step= 14, Dmax= 1.2e-06 nm, Epot= -…

my .mdp parameters are,

ntegrator = steep ; Algorithm (steep = steepest descent minimization)  
dt = 0.002 ; Energy step size  
nsteps = 1000

continuation = no  
constraints = none

cutoff-scheme = Verlet

tcoupl = Berendsen  
tc-grps = Protein Cu Cl US5F SOL  
tau-t = 0.1 0.1 0.1 0.1 0.1  
ref-t = 300.0 300.0 300.0 300.0 300.0

pcoupl = Berendsen  
tau-p = 0.5  
compressibility = 4.5e-5  
ref-p = 1.0