Dear LAMMPS users,
dear nick,
I am beginning some simulations of metal-organic frameworks, and I am trying
to figure out the best way to do this in LAMMPS. My system consists of the
elements C, H, N, O, Cu, and Cl. My initial hope was to use ReaxFF because
of its accuracy; however, perusing the author's website (as suggested in the
LAMMPS documentation) seems to indicate that a parameterization of these
particular elements has not been created.
please note that reaxff is not parameterized to elements in general,
but specific sets of elements under specific conditions. those parameters
are not necessarily transferable to other systems with the same set
of elements. if you want that kind of flexibility, you have to use ab initio
methods (in fact, that is the whole point of ab initio methods, that you
don't make any assumptions).
So I believe the universal force field (UFF) is my next best option, but it
will take me a while to input these parameters by hand from the 1992 paper
into a LAMMPS input file. I was hoping someone on here who is more familiar
with these sorts of simulations could suggest a better option if there is
one. I believe I have covered the LAMMPS documentation fairly thoroughly
i think the problem is more that you should spend some more time
on understanding how classical MD works and what its limitations are.
for example parameters are usually not given on a per element basis,
but rather on a per "atom type" basis, i.e. a given element under specific
boundary conditions. so for carbon atoms there are 10s of different types
in a typical force field. you *can* have a more generic description, but that
comes at the expense of transferability. in other words, the less specific
the atom type, the less accurate the results.
and have found a few tools for creating input files, but any knowledge from
someone else would be greatly appreciated!
building inputs for custom systems requires writing/adapting customs tools.
only for very formalized processes, e.g. proteins, one can can automate the
process somewhat using a fragment/residue database. but then again, in
many of those cases, still some customizations are required.
axel.