CP2K Plugin for ASE

A standalone CP2K calculator plugin for the Atomic Simulation Environment (ASE).

Features

• Full CP2K calculator implementation compatible with ASE
• ASE v4 plugin system integration
• Support for ASE configuration system (ase.config)

Installation

From source

git clone https://github.com/cp2k/cp2k_ase_plugin.git
cd cp2k_plugin
pip install -e .

Requirements

• ASE >= 3.23.0 (https://docs.ase-lib.org/install.html) currently using (https://gitlab.com/ase/ase/-/tree/ase4-plugins-all-calculators)
• CP2K (https://github.com/cp2k/cp2k/blob/master/INSTALL.md)

Usage

Important: Always specify a working directory via directory=... to keep output files. If directory=None (the default), a temporary directory is created and auto-cleaned on close().

Via plugin system

from ase._4.plugins import plugins

CP2K = plugins.calculators['cp2k'].implementation()
calc = CP2K(directory="/path/to/output")

Direct import

from cp2k_plugin import CP2K

calc = CP2K(directory="/path/to/output")

CP2K Executable Configuration

The CP2K executable is launched via CP2K-shell (the interactive socket-mode variant used for ASE communication). The plugin uses the following priority order to locate the command:

1. Command parameter (highest priority)

calc = CP2K(command="mpiexec -np 4 cp2k.psmp -s")

2. Class variable

CP2K.command = "mpiexec -np 4 cp2k.psmp -s"
calc = CP2K()

3. ASE configuration file

Set in ~/.config/ase/config.ini:

[cp2k]
cp2k_shell = env OMP_NUM_THREADS=1 mpiexec -np 4 /path/to/cp2k.psmp -s
cp2k_main = env OMP_NUM_THREADS=1 mpiexec -np 4 /path/to/cp2k.psmp

The cp2k_main setting is used for tests that run CP2K directly (e.g., DCD file generation).

4. Environment variable

export ASE_CP2K_COMMAND="mpiexec -np 4 cp2k.psmp -s"

5. Default (lowest priority)

If none of the above is set, the plugin defaults to:

cp2k.psmp -s

Note: The command must be resolvable via $PATH or given as an absolute path. The plugin does not search for the executable automatically.

shell mode

The default command cp2k.psmp -s launches CP2K-shell in shell mode. For file-I/O mode (batch-style), you may want to use e.g.:

cp2k.psmp -i PREFIX.inp -o PREFIX.out

However, the CP2K calculator is designed around CP2K-shell and the -s flag is required for full functionality.

Citation

If you use this plugin in your research, please cite:

• M. Iannuzzi et al., "The CP2K Program Package Made Simple," J. Phys. Chem. B, vol. 130, pp. 1237, 2026, (https://doi.org/10.1021/acs.jpcb.5c05851)
• CP2K developers (https://www.cp2k.org/)

License

LGPL-2.1-or-later

Documentation

See the doc/ directory for detailed documentation.

Testing

The tests require CP2K compiled with the toolchain. Any number of MPI processes should work, but large numbers can slow down the tests.

Configure CP2K Command

Set the CP2K executable in ~/.config/ase/config.ini:

[cp2k]
cp2k_shell = env OMP_NUM_THREADS=1 mpiexec -np 4 /path/to/build_cp2k/install/bin/cp2k.psmp -s
cp2k_main = env OMP_NUM_THREADS=1 mpiexec -np 4 /path/to/build_cp2k/install/bin/cp2k.psmp

Replace /path/to/build_cp2k/install/bin/cp2k.psmp with your actual CP2K installation path. Use OMP_NUM_THREADS=1 to avoid thread exhaustion.

Run Tests

# Activate ASE environment
source ~/venvs/ase/bin/activate

# Source CP2K environment (if using toolchain)
source /path/to/build_cp2k/install/cp2k_env

# Run tests
pytest tests/ -v

Contributing

Contributions welcome! Please open an issue or submit a pull request.