[gmx-users] Energy minimization issue

[Justin Lemkul]

On 10/16/17 5:19 AM, Khadija Amine wrote:
> Dear Gromacs users,
>
> I'm simulation a double chain protein-ligand complex using Amber force
> field. I have written parameters and generated the topology.
>
> The energy minimization of the complex gives me the following error:
>
> *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)*
> Could you please tell me what is the issue and provide some suggestions

http://www.gromacs.org/Documentation/Errors#Stepsize_too_small.2c_or_no_change_in_energy._Converged_to_machine_precision.2c_but_not_to_the_requested_precision

-Justin

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Justin A. Lemkul, Ph.D.
Assistant Professor
Virginia Tech Department of Biochemistry

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