Dear Mike,
Sounds like the infamous Exponential-6 catastrophe where the Buckingham class of potentials give negative infinity energies for small distances, thereby causing nuclear fusion...
indeed this is what happens. However, the couple of particles that give
rise to this behavior (whose indexes in the LAMMPS input file are 6998
and 13335) are 1.37 Ang apart at the beginning of the simulation. At
this distance the Buckingham potential is well into the repulsive region.
It looks like the atom 13335 is behaving as a positive particle...
Thank you for the help,
Otello
There used to be a simple fix for this (inverting the curve at small distances), but I will have to dig up some old fortran code.
Mike
From: Otello Maria Roscioni<[email protected]...>
To: [email protected]
Cc:
Sent: Tuesday, June 21, 2011 5:22 PM
Subject: [lammps-users] incorrect interaction
Dear Steve, dear LAMMPS users,
I have run several MD simulations using the same settings, with no
problem at all. However, in one case I found a strange error: at the
very beginning of the simulation, two oxygen atoms (which should
be kept separated by a Buckingham potential plus Coulomb repulsion) get
in contact with one another, thus
making the calculation to fail.
I have checked the structure and it looks fine. If somebody wants to
have a look at my simulation, all
the relevant files are here:
http://dl.dropbox.com/u/4235054/s01_hyd2.tgz
Thank you for the help,
Otello
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