[gmx-users] Error:EM did not converge while using polarizable ion

Justin Lemkul jalemkul at vt.edu
Wed Aug 5 01:23:53 CEST 2015

On 8/4/15 5:40 PM, 折晓会 wrote:
> Thank you professor Justin and Chaban for helpful suggestions!
> In the topology file, I choose "POL2" for water and anions, and the simulation seems working well now. The results of energy minimization are:

Hyperpolarization protection is often needed in polarizable simulations, so the 
use of "POL2" in the virtualchemistry.org files makes a big difference.  Without 
this effect, polarization catastrophe is common.

> Steepest Descents converged to machine precision in 8755 steps,
> but did not reach the requested Fmax < 1.
> Potential Energy  = -3.0687320e+04
> Maximum force     =  1.7012895e+02 on atom 2499
> Norm of force     =  7.2500138e+00
> Are the results reasonable for the polarizable models? I am wondering why the final force does not match Fmax < 1.

You'll never reach such a tolerance for the whole system using steepest descent 
in singe precision.  That said, the outcome is perfectly reasonable.  The value 
of emtol = 1 in the context of the Drudes/shells is that the maximum allowable 
force on the Drudes themselves is set to 1 during the run for the purposes of 
the SCF relaxation.



Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

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


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