.. _lammps_potential:

================
LAMMPS Potential
================

In order to use the LAMMPS potential you must first build the serial library
version of LAMMPS. This can be done by following the instructions in the
`lammps documentation <https://lammps.sandia.gov/doc/Manual.html>`_ . For
most cases executing these commands from the LAMMPS ``src`` folder should work::

    $ cd STUBS
    $ make
    $ cd ..
    $ make yes-manybody serial mode=lib

Once you have compiled the library copy ``liblammps_serial.a`` and
``STUBS/libmpi_stubs.a`` to the client/potentials/LAMMPS directory in the Eon
source code.  The Eon client can then be built like so::

    $ make LAMMPS_POT=1

After setting the potential to ``lammps`` in ``config.ini`` you need to place a
LAMMPS input file in the ``potfiles`` directory in your simulation. This file should
be named ``in.lammps`` and it needs to specify what potential LAMMPS should use.
Here is an example in.lammps file that uses the morse potential::

    pair_style morse 9.5 #morse potential with 9.5 Angstrom cutoff
    pair_coeff * * 0.7102 1.6047 2.797 #specify parameters
    pair_modify shift yes #shift the potential to be zero at the cutoff


MEAM
====

If you compiled LAMMPS with the MEAM package you need to copy
``lib/meam/libmeam.a`` from the LAMMPS directory to
``potentials/LAMMPS`` in EON. After that, add the following line to
``client/Makefile``::

    LDFLAGS += potentials/LAMMPS/libmeam.a

OpenMP
======

Compile LAMMPS with the USER-OMP package. Then add the following line
to ``client/Makefile``::

    LDFLAGS += -fopenmp

See below for setting the number of threads.

Options
=======

**lammps_logging**: This option enables/disables the LAMMPS logfile. If enabled
LAMMPS will log to the file ``log.lammps``.

    default: ``false``

**lammps_threads**: Controls how many threads to use if LAMMPS has been
compiled with OpenMP support via the USER-OMP LAMMPS package.

    default: ``0``


Notes for Intel Compilers
=========================

To build the LAMMPS serial library with Intel compilers, make these following
modifications (from the LAMMPS ``src`` directory):

* ``STUBS/Makefile``       : set ``CC`` to ``icpc`` or ``icpx``
* ``MAKE/Makefile.serial`` : set ``CC`` and ``LINK`` to ``icpc`` or ``icpx``

To build the EON client with Intel compilers, make these following modifications
to EON's ``client/Makefile``:

* Set ``CC`` to ``icc``
* Set ``CXX`` to ``icpc``
* Add ``-std=c++11`` to ``CXXFLAGS``
* In the ``Fortran compiler settings`` section, comment out the ``FC``, ``FFLAGS``, ``FAR``, and ``LDFLAGS`` lines under ``#gfortran``, and uncomment them under ``#ifort``