AMBER Archive (2003)

Subject: Minimization problem w/ counter-ion !

From: Marco Preto (mcpreto_at_fc.up.pt)
Date: Wed Oct 30 2002 - 20:54:27 CST

Dear Amber users:

I'm trying to run a minimization of a solvent box (with my solute and
Cl- fixed) to get a better starting point to the equilibration dynamic
run of my system. Unfortunatly I'm having trouble with the electrostatic
interactions (this value goes to so negative magnitude that the format
is not suficient to writ it and my output comes like ***********. I've
tryed to put the counter ion using addions and when that did not work I
tryed to put it manually on my system, in diferent positions, but the
calculations allways stoped with a segmentation fault, during this
minimization.
I guess the problem is with the counter ion because I have been running
the same protocol on non charged solutes and it runs without anyproblem
at all!
I'm using Amber6 and my solute is a small peptide (8 residues). Here is
the minimization input:

&cntrl
imin=1, maxcyc=200000, cut=12, igb=0,
ntb=1, ntpr=1000, ncyc=2000,
ibelly=1, ntwx=100,
&end
Group input for moving atoms
RES 10 3846
END
END

Res 10 to 3846 are my water molecules! I know that running Ewald and
belly simultaniously is not correct but that's not the reason why the
calculation is dieing!

Can anyone bring some light to this problem?

Sincerely yours 

-- 
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 Marco A. C. Preto               |"Quantum temporis lucratur qui non
 PH.D. student                   |aspicit quod vicinus dicit, agit
 Theoretical Chemistry group     |vel cogitat, sed tantum quod ipse
 Chemistry Deparmant - FCUP      |agit ad id iustum et sanctum 
 Porto, Portugal                 |reddendum"
_________________________________|
                                 |   from my homonimous
email: mcpreto_at_fc.up.pt          |  
                                 |                 Marcus Aurelius
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