This directory has source files to build a library that LAMMPS links against when using the REAX package.

When you are done building this library, two files should exist in this directory:

libreax.a the library LAMMPS will link against Makefile.lammps settings the LAMMPS Makefile will import

The latter file will have settings like this (can be omitted if blank):

reax_SYSINC = reax_SYSLIB = -lgfortran reax_SYSPATH =

SYSINC is for settings needed to compile LAMMPS source files SYSLIB is for additional system libraries needed by this package SYSPATH is the path(s) to where those libraries are

You must insure these settings are correct for your system, else the LAMMPS build will likely fail.

Note that the source files for this library are Fortran. LAMMPS is built with a C++ compiler/linker. Thus you need to insure the settings above enable usage of a Fortran library by a C++ program.

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ReaxFF library

Aidan Thompson, Sandia National Labs athomps at sandia.gov Jan 2008

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This library is an implementation of the ReaxFF potential, specifically designed to work with LAMMPS. It is derived from Adri van Duin's original serial code, with intervening incarnations in CMDF and GRASP.

This library can be built with any decent Fortran compiler, before LAMMPS is built, so LAMMPS can link against it. The compiler must produce object files compatible with the LAMMPS C++ compiler. If not, the LAMMPS build will fail during linking.

Build the library using one of the provided Makefiles or create your own, specific to your compiler and system. For example:

make -f Makefile.g95

If the build is successful, you should end up with a libreax.a file.

Note that the include file reax_defs.h is used by both the ReaxFF library source files and the LAMMPS pair_reax.cpp source file (from module REAX). It contains dimensions of statically-allocated arrays created by the ReaxFF library. The size of these arrays must be set small enough to avoid exceeding the available machine memory, and large enough to fit the actual data generated by ReaxFF. If you change the values in reax_defs.h, you must first rebuild the library and then rebuild LAMMPS.

This library is called by functions in pair_reax.cpp. The C++ to FORTRAN function calls in pair_reax.cpp assume that FORTRAN object names are converted to C object names by appending an underscore character. This is generally the case, but on machines that do not conform to this convention, you will need to modify either the C++ code or your compiler settings. The name conversion is handled by the preprocessor macro called FORTRAN in the file pair_reax_fortran.h, which is included by pair_reax.cpp. Different definitions of this macro can be obtained by adding a machine-specific macro definition to the CCFLAGS variable in your your LAMMPS Makefile e.g. -D_IBM. See pair_reax_fortran.h for more info.