# Install LAMMPS

There are two ways to install LAMMPS: the built-in mode and the plugin mode. The built-in mode builds LAMMPS along with the DeePMD-kit and DeePMD-kit will be loaded automatically when running LAMMPS. The plugin mode builds LAMMPS and a plugin separately, so one needs to use `plugin load` command to load the DeePMD-kit's LAMMPS plugin library.

## Install LAMMPS's DeePMD-kit module (built-in mode)

Before following this section, [DeePMD-kit C++ interface](install-from-source.md) should have be installed.

DeePMD-kit provides a module for running MD simulations with LAMMPS. Now make the DeePMD-kit module for LAMMPS.

```bash
cd $deepmd_source_dir/source/build
make lammps
```

DeePMD-kit will generate a module called `USER-DEEPMD` in the `build` directory, which supports either double or single float precision interface. Now download the LAMMPS code, and uncompress it.

```bash
cd /some/workspace
wget https://github.com/lammps/lammps/archive/stable_29Aug2024_update1.tar.gz
tar xf stable_29Aug2024_update1.tar.gz
```

The source code of LAMMPS is stored in the directory `lammps-stable_29Aug2024_update1`.

Then, you can [build LAMMPS](https://docs.lammps.org/Build.html) with either make or CMake.

### With make

Now go into the LAMMPS code and copy the DeePMD-kit module like this

```bash
cd lammps-stable_29Aug2024_update1/src/
cp -r $deepmd_source_dir/source/build/USER-DEEPMD .
make yes-kspace
make yes-extra-fix
make yes-user-deepmd
```

You can enable any other package you want. Now build LAMMPS

```bash
make mpi -j4
```

If everything works fine, you will end up with an executable `lmp_mpi`.

```bash
./lmp_mpi -h
```

The DeePMD-kit module can be removed from the LAMMPS source code by

```bash
make no-user-deepmd
```

### With CMake

Now go into the LAMMPS directory and create a directory called `build`:

```bash
mkdir -p lammps-stable_29Aug2024_update1/build/
cd lammps-stable_29Aug2024_update1/build/
```

Patch the LAMMPS `CMakeLists.txt` file:

```bash
echo "include(${deepmd_source_dir}/source/lmp/builtin.cmake)" >> ../cmake/CMakeLists.txt
```

It's expected to see one extra line in the end of `CMakeLists.txt`.

Now build LAMMPS. You can install any other package you want.

```bash
cmake -D LAMMPS_INSTALL_RPATH=ON -D BUILD_SHARED_LIBS=yes -D CMAKE_INSTALL_PREFIX=${deepmd_root} -DCMAKE_PREFIX_PATH=${deepmd_root} ../cmake
make -j4
make install
```

If everything works fine, you will end up with an executable `${deepmd_root}/bin/lmp`.

```bash
${deepmd_root}/bin/lmp -h
```

## Install LAMMPS (plugin mode)

Starting from `8Apr2021`, LAMMPS also provides a plugin mode, allowing one to build LAMMPS and a plugin separately.

Now download the LAMMPS code (`8Apr2021` or later), and uncompress it:

```bash
cd /some/workspace
wget https://github.com/lammps/lammps/archive/stable_29Aug2024_update1.tar.gz
tar xf stable_29Aug2024_update1.tar.gz
```

The source code of LAMMPS is stored in the directory `lammps-stable_29Aug2024_update1`. The directory of the source code should be specified as the CMAKE argument `LAMMPS_SOURCE_ROOT` during installation of the DeePMD-kit C++ interface. Now go into the LAMMPS directory and create a directory called `build`

```bash
mkdir -p lammps-stable_29Aug2024_update1/build/
cd lammps-stable_29Aug2024_update1/build/
```

Now build LAMMPS. Note that `PLUGIN` must be enabled, and `BUILD_SHARED_LIBS` must be set to `yes`. You can install any other package you want.

```bash
cmake -D PKG_PLUGIN=ON -D LAMMPS_INSTALL_RPATH=ON -D BUILD_SHARED_LIBS=yes -D CMAKE_INSTALL_PREFIX=${deepmd_root} -D CMAKE_INSTALL_LIBDIR=lib -D CMAKE_INSTALL_FULL_LIBDIR=${deepmd_root}/lib ../cmake
make -j4
make install
```

If everything works fine, you will end up with an executable `${deepmd_root}/bin/lmp`.

```bash
${deepmd_root}/bin/lmp -h
```

:::{note}
If `${tensorflow_root}`, `${deepmd_root}`, or the path to TensorFlow Python package if applicable is different from the prefix of LAMMPS, you need to append the library path to [`RUNPATH`](https://man7.org/linux/man-pages/man8/ld.so.8.html) of `liblammps.so`. For example, use patchelf >= 0.13

```sh
patchelf --add-rpath "${tensorflow_root}/lib" liblammps.so
```

:::