AMBER Archive (2007)

Subject: Re: AMBER: convergence criterion not reached

From: David A. Case (case_at_scripps.edu)
Date: Mon Jul 02 2007 - 20:14:53 CDT

On Tue, Jul 03, 2007, Jena M wrote:
>
>
> I want to move a ligand toward a protein residue in various steps using
> distance restraints, and then calculate the energy at each step through a
> minimisation. I want to use a strict 0.0001 kcal/mol convergence criterion.
> However at the first step the minimisation ended with the following message:
>
> .... RESTARTED DUE TO LINMIN FAILURE ...
>
> ***** REPEATED LINMIN FAILURE *****
>
>
> FINAL RESULTS
>
>
>
> NSTEP ENERGY RMS GMAX NAME NUMBER
> 822 -5.0298E+05 6.1915E-04 1.0122E-01 HB2 10744

This is expected. Look at the FAQ's on the Amber page, or search for LINMIN
failure using our search box. One possible thing to try is to set dsum_tol
in the &ewald namelist to 0.000001, which may help.

I will note that for a periodic (I assume solvated) system, finding a precise
minimum (including the positions of all solvent molecules) may not be all that
useful an exercise. (But of course, I don't know what you are really trying
to do here.....)

...good luck....dac

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