On the REAXX force field

Dear all,

My aim is to do a MD on a polymer that I have and I am thinking of using the REAXX force field. I want to know how to produce the files with all the parameters needed (bonds, dihedrals) to be fed into LAMMPS to start my modeling. Anywhere where I can find ABC information on that?

Thanks a lot


You don't need to define any bond/angle/dyhedral etc as reaxff does
that for you automatically. How about you start by reading the
original reaxff paper and the lammps doc on the topic to enlighten
yourself a bit?

add on: the only file you need in lammps is the "ffield.reax" (and the
corresponding reference to it within the lammps input file) containing
the reaxff parameters, i.e. those designed for the given class of
systems you intend to model: hydrocarbons, metallic oxides, etc...


thanks. I started reading the REAXXFF documentation. My first intention is that one has to produce the .reax file using the REAXX code , is that correct? If so, is it a free code and from where can I download it. My polymer has Cl, N, O, H and C in it so hopefully it works in producing the parameters correctly.


The ffield.reax is an external file that is not self-generated by
Lammps. As I said, this file contains the parameters that the reaxff
implementation needs to read in order to become functional. Generating
the parameters for such a file could be quite complex. You best shot
is to look in the literature to see if anyone has published a paper
that deals with reaxff and the polymer you intend to study. Lammps
comes a few of reaxff parameter files but I'm not sure if any of those
is specially tailored to your system.
Papers where a new reaxff parametrization is developed usually
include a copy of the ffield.reax in their "Supporting Info" section.
The other avenue is to look for reaxff databases on the web or contact
Adri C. T. van Duin directly and see if they have developed a reaxff
parametrization for your specific system.