On 6/3/13 8:12 PM, Someone Else wrote:
Thanks for the answer.
You're introducing atomic overlap and thus an energetic singularity from
the infinite Coulombic attraction.
Is there anything I can do with this?
I posted this question because I'm trying to run a Monte Carlo simulation
of a water box but eventually it finds the global energy minimum (-Inf) and
can't escape from it.
That sounds like something done outside of Gromacs, is it not? I would think
that properly accounting for Coulombic interactions would have prevented this
from occurring, but I don't do MC so I can't go beyond speculation.
-Justin
2013/6/4 Justin Lemkul [via GROMACS] ml-node+s5086n5008760...@n6.nabble.com
On 6/3/13 7:49 PM, tnorgd wrote:
Dear group,
I am not sure how SPC energy actually works - is there really just one
VdW
interaction - just between two oxygen atoms?
Yep. A lot of force fields work like that. Given the size of H atoms
relative
to their heavy atom counterparts, the heavy atom to which they are
connected
generally governs the vdW interactions.
If so, when I place a hydrogen atom of one water molecule at the
location of
the oxygen from another water,
the two oxygens are separated by the distance of H-O bond length i.e.
1.0A.
The only VdW interaction is repulsive but finite (and equal ~4E6) but
the
electrostatic between H and O is -Inf = 1/0.0
What's wrong?
Nothing. That makes perfect sense. You're introducing atomic overlap and
thus
an energetic singularity from the infinite Coulombic attraction.
-Justin
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Virginia Tech
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Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
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