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:
|LICENSE||GNU General Public License (GPL)|
|cmake||CMake build files|
|examples||simple test problems|
|lib||additional provided or external libraries|
|potentials||interatomic potential files|
|python||Python wrapper on LAMMPS|
|tools||pre- and post-processing tools|
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.