AMBER Archive (2002)

Subject: Re: vlimit exceeded

From: Carlos Simmerling (carlos.simmerling_at_sunysb.edu)
Date: Wed Jun 12 2002 - 06:42:14 CDT

try a much smaller force constant, like 1.0
CS
===================================================================
Carlos L. Simmerling, Ph.D.
Assistant Professor Phone: (631) 632-1336
Center for Structural Biology Fax: (631) 632-1555
SUNY at Stony Brook Web: http://comp.chem.stonybrook.edu/carlos
Stony Brook, NY 11794-5115 E-mail: carlos.simmerling_at_stonybrook.edu
===================================================================

----- Original Message -----
From: "A. Hungie" <hungie01_at_hotmail.com>
To: <amber_at_heimdal.compchem.ucsf.edu>
Sent: Wednesday, June 12, 2002 5:49 AM
Subject: vlimit exceeded

> Dear Amber users,
>
> I tried to run MD by constraint some atoms (NTR=1). I got an error message
> "vlimit exceeded" at beginning of dynamics. An input and output are as
below
>
> ==> mdin
> *********************
> dynamics
> &cntrl
> ntx = 1, irest = 0, nmropt = 0,
> imin = 0, nstlim = 10000,
> dt = 0.002,
> ntcm = 1, nscm = 2500,
> ntpr = 20, ntwr = 500,
> ntb = 2, ntp = 1,
> ntc = 2, tol = 0.000001,
> ntf = 2,
> ibelly = 0, ntr = 1,
> temp0 = 300.0, tempi = 300.0,
> ntt = 1, vlimit = 20.0,
> &end
>
> &ewald
> a = 42.2774713, b = 43.6275041, c = 67.0496168,
> nfft1 = 45, nfft2 = 45, nfft3 = 72,
> &end
> Constrain G6
> 5000.0
> ATOM 171 185
> END
> Constrain G8
> 5000.0
> ATOM 236 250
> END
> END
>
> *********************
> ==> output
>
> NSTEP = 0 TIME(PS) = 0.000 TEMP(K) = 435.47 PRESS = -5283.28
> Etot = -49484.9577 EKtot = 10822.6043 EPtot = -60307.5620
> .
> .
> . Density = 1.0308
> Ewald error estimate: 0.1386E-03
> -----------------------------------------------------------
>
> vlimit exceeded for step 2; vmax = 271.116268
>
> COORDINATE RESETTING CANNOT BE ACCOMPLISHED,
> DEVIATION IS TOO LARGE
> NITER, NIT, LL, I AND J ARE : 0 1 65 181 182
>
> *************
>
> However, when I changed NTR from 1 to 0 (no constrain) and removed
constrain
> parameters (last 10 lines in mdin), it worked fine.
>
> Could you please give me any suggestion?
>
> Many thanks in advance.
>
> Hungie.
>
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