I have a very simple system consisting of a linear chain of atoms
interacting via harmonic bonds with periodic boundary conditions. My
problem is that I'm facing an inconsistent behaviour in two versions of
lammps. The version from 17.Jun.2012 behaves as I expect and the chain
remains streched throughout the simulation, with the end atoms
apparently interacting with the images of each other. Instead, in the
latest version 09.Sept.2013, the system appears to immediately collapse
into a ring, almost as if ignoring the interaction with periodic images.
I understand there have been some changes in the way bonds across
periodic boundaries are dealt with, but it seems that the latest version
does not treat these appropriately. The presence of these bonds between
images should prevent the chain from collapsing into a ring, as it was
the case in the 17.Jun.2012 version.
I am attaching a simple input script and data file which reproduce the
My question is: is the current version of lammps really producing the
"correct" behaviour? If so, how is it then possible to simulate a simple
harmonic chain with periodic boundary conditions?
in.bond.lj (944 Bytes)
data.1d.chain (546 Bytes)