On 7/25/14, 11:22 AM, Tamas Karpati wrote:
Dear Justin,

Does your topology specify the proper intramolecular exclusions?  What
is(are) the molecule(s)?

No bonds, no exclusions. The whole crystal is modelled by ions
interacting via forces of the Coulomb and Buckingham types.
In fact, there is an X-Y-X angle force type which does have an
effect on forces and energy. Shell particles, on the other hand,
are defined via the [polarization] section as quasi-bonds. That's all.


Coulombic interactions fail at short distances; you probably need to apply Thole screening to avoid polarization catastrophe. Ions are particularly problematic in this regard.

Try nstlist = 1.  The shell positions are solved via SCF (EM), so you need
to update the neighbor list very frequently.

Thanks for the trick. Tried but to no avail (very same results).
Although shells should have their weight in the model, I expect
them not to frequently change partner -each is ultimately connected
to its core atomic site.
In addition, there are no more bonds in the system i, thus, don't
see the point in regenerating pairs. Is there a process -I should
get to know about- which autogenerates bonds?


If your model doesn't use them, then there's nothing to be done here. I was asking about bonded structure and exclusions and such because of the Thole issue I noted above.

-Justin

--
==================================================

Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 601
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalem...@outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul

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