Re: [AMBER] unexpected "vlimit exceeded for step" error

From: case <>
Date: Mon, 21 Jun 2010 13:48:29 -0400

On Mon, Jun 21, 2010, Cristina Sisu wrote:
> When I heat the system however one of the
> systems is behaving very strangely, in the way that after my first step
> I get the following errors:
> > vlimit exceeded for step 2; vmax = 33.0050
> > vlimit exceeded for step 3; vmax = 25.9657

When you have vlimit errors right at the beginning, you probably have some
bad initial contacts, than minimization did not get rid of. These can be hard
to find sometime, but look in the vicinity of what is different between the
two structures.
> > nstlim=25000,dt=0.002,

It's much safer to heat iwth dt=0.001.

> > cut=11.0, ntb=1,

Why are you using such a large value for "cut"? It's probably unrelated to
your problems, but you are just wasting computer time with this. Consider
sticking to the default value.

> > nmropt=1,
> > /
> > &wt TYPE='TEMP0', istep1=0, istep2=25000,
> > value1=0.1, value2=300.0, /
> > &wt TYPE='END' /

I'd recommend leaving off the nmropt=1 stuff, which might cause problems(?)

But your best hope is to get the system equilibrated with a shorter time step.

...good luck...dac

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Received on Mon Jun 21 2010 - 11:00:03 PDT
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