[gmx-users] Energy minimization has stopped....

[Justin Lemkul]

On 11/5/13 6:28 AM, Kalyanashis Jana wrote:
> Hi,
>    Whenever I am trying to do position retrained MD run, It has been stopped
> at middle of the MD run. I have given the following error. Can you please
> suggest me something to resolve this error?
> Energy minimization has stopped, but the forces havenot converged to the
> requested precision Fmax < 100 (whichmay not be possible for your system).
> It
> stoppedbecause the algorithm tried to make a new step whose sizewas too
> small, or there was no change in the energy sincelast step. Either way, we
> regard the minimization asconverged to within the available machine
> precision,given your starting configuration and EM parameters.
>
> Double precision normally gives you higher accuracy, butthis is often not
> needed for preparing to run moleculardynamics.
>
> writing lowest energy coordinates.
>
> Steepest Descents converged to machine precision in 20514 steps,
> but did not reach the requested Fmax < 100.
> Potential Energy  = -9.9811250e+06
> Maximum force     =  6.1228135e+03 on atom 15461
> Norm of force     =  1.4393512e+01
>

Visualize the output, specifically near atom 15461.  The forces there are too 
high and cannot be resolved further.  Any attempt to use these coordinates for 
dynamics will probably lead to a crash.

-Justin

-- 
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Justin A. Lemkul, Ph.D.
Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 601
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441

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