Re: [AMBER] Newton-Raphson minimization

From: case <case.biomaps.rutgers.edu>
Date: Mon, 11 Oct 2010 07:48:01 -0400

On Mon, Oct 11, 2010, fancy2012 wrote:
>
> And I want to do some Newton-Raphson minimizations,

> &data
> ntrun = 4, cut = 10,
> drms = 0.0001, maxcyc = 5000,
           ^^^^^^^^ ^^^^^^^^

These values are wrong. You should not start Newton-Raphson (if you need it
at all) until the RMS gradient is lower than 10**-4 or so. And the number
of cycles should be something like 10 or 20: this is a very expensive type
of calculation. Why do you think you even need it?

> It doesn't work because "ASSERTion ' ier == 0 ' failed in nmode.f at
> line 106."

You don't have enough memory to run the calculation. You don't say
how big your system is, but anything over 10,000 atoms (often less)
requires a *lot* of available memory. Consider using xmin to minimize
your structures instead. Be sure to note also that nmode only works
for vacuum force fields, and so has a very limited range on utility; we
don't even provide documentation any more, since other options (e.g. the
"nmode()" function in NAB) are generally much more useful.

....dac


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Received on Mon Oct 11 2010 - 05:00:05 PDT
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