This package contains a implementation for LAMMPS of the ReaxFF force field. ReaxFF uses distance-dependent bond-order functions to represent the contributions of chemical bonding to the potential energy. It was originally developed by Adri van Duin and the Goddard group at CalTech.

The USER-REAXC version of ReaxFF (pair_style reax/c), implemented in C, should give identical or very similar results to pair_style reax, which is a ReaxFF implementation on top of a Fortran library, a version of which library was originally authored by Adri van Duin.

The reax/c version should be somewhat faster and more scalable, particularly with respect to the charge equilibration calculation. It should also be easier to build and use since there are no complicating issues with Fortran memory allocation or linking to a Fortran library.

For technical details about this implementation of ReaxFF, see this paper:

Parallel and Scalable Reactive Molecular Dynamics: Numerical Methods and Algorithmic Techniques, H. M. Aktulga, J. C. Fogarty, S. A. Pandit, A. Y. Grama, Parallel Computing, in press (2011).

See the doc page for the pair_style reax/c command for details of how to use it in LAMMPS.

The person who created this package is Hasan Metin Aktulga (hmaktulga at lbl.gov), while at Purdue University. Contact him directly, or Aidan Thompson at Sandia (athomps at sandia.gov), if you have questions.

Thanks to Steve Plimpton and Aidan Thompson for their input on the LAMMPS architecture and for their help in understanding and customizing some of the required LAMMPS interfaces.

Note that files in the package with names starting with "reaxc" are from PuReMD, the Purdue ReaxFF Molecular Dynamics Program. Its copyright info and authorship info are listed below.

The reaxc files in this directory have the following header:

PuReMD - Purdue ReaxFF Molecular Dynamics Program

Copyright (2010) Purdue University
Hasan Metin Aktulga, hmaktulga@lbl.gov
Joseph Fogarty, jcfogart@mail.usf.edu
Sagar Pandit, pandit@usf.edu
Ananth Y Grama, ayg@cs.purdue.edu

Please cite the related publication:
H. M. Aktulga, J. C. Fogarty, S. A. Pandit, A. Y. Grama,
"Parallel Reactive Molecular Dynamics: Numerical Methods and
Algorithmic Techniques", Parallel Computing, in press.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of 
the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  
See the GNU General Public License for more details:
<http://www.gnu.org/licenses/>.