2. Install LAMMPS

You can download LAMMPS as an executable or as source code.

With source code, you also have to build LAMMPS. But you have more flexibility as to what features to include or exclude in the build. If you plan to modify or extend LAMMPS, then you need the source code.

These are the files and sub-directories in the LAMMPS distribution:

README

Short description of the LAMMPS package

LICENSE

GNU General Public License (GPL)

bench

benchmark problems

cmake

CMake build files

doc

documentation

examples

simple test problems

fortran

Fortran wrapper for LAMMPS

lib

additional provided or external libraries

potentials

interatomic potential files

python

Python wrappers for LAMMPS

src

source files

tools

pre- and post-processing tools

unittest

sources and inputs for testing LAMMPS

You will have all of these if you download source. You will only have some of them if you download executables, as explained on the pages listed above.