LAMMPS NNP interface


The LAMMPS interface adds the neural network potential method in LAMMPS. Hence, one can use a previously fitted NNP to predict energies and forces and use LAMMPS to propagate an MD simulation. LAMMPS parallelization via MPI is fully supported.

Build instructions

Automatic build


The automatic compilation will only work on Unix-like systems as it relies on tools such as sed and tar.

For convenience the main makefile provides the compilation target lammps-nnp which will automatically download LAMMPS (version stable_3Mar2020 from the GitHub releases page) into the interface directory, unpack it to lammps-nnp, add the necessary n2p2 files to it and compile the LAMMPS mpi target. Finally, the binary lmp_mpi will be copied to the n2p2 bin directory. Hence, compiling LAMMPS with NNP support is as easy as typing

make lammps-nnp

in the n2p2 src directory. Uninstall with make clean-lammps-nnp.


Before compiling the LAMMPS makefile (src/MAKE/Makefile.mpi) will be altered to use the compiler and flags from the n2p2 target makefile (default: makefile.gnu).

If this procedure fails or you prefer to add NNP support to an existing LAMMPS installation somewhere else in your system please follow the manual build instructions below.

Manual build

To build LAMMPS with support for neural network potentials follow these steps: First, build the required libraries:

cd src
make libnnpif

For dynamic linking add the argument MODE=shared.


If dynamic linking (make libnnpif MODE=shared) is used, you need to make the NNP libraries visibile in your system, e.g. add this line in your .bashrc:

export LD_LIBRARY_PATH=<path-to-n2p2>/lib:${LD_LIBRARY_PATH}

Then change to the LAMMPS root directory and link the repository root folder to the lib subdirectory:

cd <path-to-LAMMPS>/
ln -s <path-to-n2p2> lib/nnp


The link should be named nnp, NOT n2p2!

Next, copy the USER-NNP package to the LAMMPS source directory:

cp -r src/interface/LAMMPS/src/USER-NNP <path-to-LAMMPS>/src

Finally activate the NNP package in LAMMPS:

cd <path-to-LAMMPS>/src
make yes-user-nnp

Now, you can compile LAMMPS for your target as usual:

make <target>


If you want to compile a serial version of LAMMPS with neural network potential support, the use of MPI needs to be deactivated for libnnpif. Just enable the -DNOMPI option in the settings makefile of your choice, e.g. makefile.gnu.


The neural network potential method is introduced in the context of a pair style named nnp. LAMMPS comes with a large collection of these pair styles, e.g. for a LJ or Tersoff potential, look here for more information. The setup of a nnp pair style is done by issuing two commands: pair_style and pair_coeff. See this page for a detailed description.