March Module of the Month: n2p2 – Improved link to HPC MD software


This module improves the connection of n2p2 to HPC software, in particular to LAMMPS, by creating a pull request to the official LAMMPS repository. Furthermore, the build process for the n2p2 interface library is enhanced to allow for a selective activation of different interfaces. A first application is also supported: the user contribution of an n2p2 interface to CabanaMD which uses Kokkos to drive MD simulations with NNP support on GPUs.


This module is based on n2p2 (NeuralNetworkPotentialPackage), a C++ code for generation and application of neural network potentials used in molecular dynamics simulations. The source code and documentation are located here:

Although n2p2 was already shipped with source files for patching LAMMPS before (see here) , the build process required manual intervention of users. To avoid this in future versions of LAMMPS a pull request was created to include the n2p2/LAMMPS interface by default as a user package. In order to conform with LAMMPS contribution guidelines multiple issues were resolved, triggering these changes/additions to LAMMPS and n2p2:

• Modify the CMake build process to search and include n2p2

• Create additional documentation about the build settings

• Create a suitable example which can be shipped with LAMMPS

• Adapt documentation of the LAMMPS “pair_style nnp” command

• Change n2p2 to conformwith LAMMPS “bigbig” settings

• Change the source files “pair_nnp.(cpp/h)” to conform with the LAMMPS coding style

Furthermore, the n2p2 build system was adapted to allow for multiple interfaces to other software packages, with an option to select only those of interest to the user. As a first application, the user contributed CabanaMD interface was integrated in the new build process. CabanaMD is an ECP proxy application which makes use of the Kokkos performance portability library and n2p2 to port neural network potentials in MD simulations to GPUs and other HPC hardware.

Practical applications

The integration of neural network potentials directly in LAMMPS via a user package with linkage to n2p2 will greatly enhance the visibility and user experience. User will also be able to retrieve information about the neural network potential method and its use directly on the LAMMPS documentation page. Modifying the n2p2 build process to allow for multiple interfacing software simplifies the development of CabanaMD. This contribution of n2p2 users can be viewed as a precursor of a Kokkos implementation of NNPs in LAMMPS. Ultimately, such an addition to n2p2/LAMMPS would be of great value for the community as it would allow for running molecular dynamics simulation with NNPs on GPUs.

A success story on the E-CAM developments on n2p2 is also available, which explains in more detail all the practical applications from this work: Implementation of High-Dimensional Neural Network Potentials .

Documentation and source Code

Module documentation is available on our software repository here.