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Welcome to ShakeNBreak!#

ShakeNBreak (SnB) is a defect structure-searching method employing chemically-guided bond distortions to locate ground-state and metastable structures of point defects in solid materials. ShakeNBreak logo

Main features include:

  1. Defect structure generation:

    • Automatic generation of distorted structures for input defects

    • Optionally, input file generation for geometry optimisation with several codes (VASP, CP2K, Quantum-Espresso, CASTEP & FHI-aims)

  2. Analysis:

    • Parsing of geometry relaxation results

    • Plotting of final energies versus distortion to demonstrate what energy-lowering reconstructions have been identified

    • Coordination & bonding analysis to investigate the physico-chemical factors driving an energy-lowering distortion

    • Magnetisation analysis (currently only supported for VASP)

The code currently supports VASP, CP2K, Quantum-Espresso, CASTEP and FHI-aims. Code contributions to support additional solid-state packages are welcome!


_images/SnB_Supercell_Schematic_PES_2sec_Compressed.gif

Installation#

ShakeNBreak can be installed using pip:

pip install --user shakenbreak

If using VASP, in order for ShakeNBreak to automatically generate the pseudopotential input files (POTCARs), your local VASP pseudopotential directory must be set in the pymatgen configuration file $HOME/.pmgrc.yaml as follows:

PMG_VASP_PSP_DIR: <Path to VASP pseudopotential top directory>

Within your VASP pseudopotential top directory, you should have a folder named POT_GGA_PAW_PBE which contains the POTCAR.X(.gz) files (in this case for PBE POTCARs). More details given here.

Developer installation#

For development work, ShakeNBreak can also be installed from a copy of the source directory:

  1. Download ShakeNBreak source code using the command:

    git clone https://github.com/SMTG-UCL/ShakeNBreak
    
  2. Navigate to root directory:

    cd ShakeNBreak
    
  3. Install the code, using the command:

    pip install -e .
    

    This command tries to obtain the required packages and their dependencies and install them automatically.

Usage#

Python API#

ShakeNBreak can be used through a Python API, as exemplified in the SnB Python API Tutorial.

Command line interface#

Alternatively, the code can be used via the command line.


_images/SnB_CLI.gif

The functions provided include:

  • snb-generate: Generate distorted structures for a given defect

  • snb-generate_all: Generate distorted structures for all defects present int the specified/current directory

  • snb-run: Submit geometry relaxations to the HPC scheduler

  • snb-parse: Parse the results of the geometry relaxations and write them to a yaml file

  • snb-analyse: Generate csv files with energies and structural differences between the final configurations

  • snb-plot: Generate plots of energy vs distortion, with the option to include a colorbar to quantify structural differences

  • snb-regenerate: Identify defect species undergoing energy-lowering distortions and test these distortions for the other charge states of the defect

  • snb-groundstate: Save the ground state structures to a Groundstate directory for continuation runs

More information about each function and its inputs/outputs are available from the CLI section of the docs or using -h help option (e.g. snb -h).

We recommend at least looking through the Tutorials when first starting to use ShakeNBreak, to familiarise yourself with the full functionality and workflow.

Code Compatibility#

ShakeNBreak is built to natively function using pymatgen Defect objects (docs available here) and be compatible with the most recent version of pymatgen. If you are receiving pymatgen-related errors when using ShakeNBreak, you may need to update pymatgen and/or ShakeNBreak, which can be done with:

pip install --upgrade pymatgen shakenbreak

ShakeNBreak can take pymatgen Defect objects as input (to then generate the trial distorted structures), but also can take in pymatgen Structure objects, doped defect dictionaries or structure files (e.g. POSCARs for VASP) as inputs. As such, it should be compatible with any defect code (such as doped, pydefect, PyCDT, PyLada, DASP, Spinney, DefAP, PyDEF…) that generates these files. Please let us know if you have any issues with compatibility, or if you would like to see any additional features added to ShakeNBreak to make it more compatible with your code.

Acknowledgements#

ShakeNBreak has benefitted from feedback from many members of the Walsh and Scanlon research groups who have used / are using it in their work, including Adair Nicolson, Xinwei Wang, Katarina Brlec, Joe Willis, Zhenzhu Li, Jiayi Cen, Lavan Ganeshkumar, Daniel Sykes, Luisa Herring-Rodriguez, Alex Squires, Sabrine Hachmiouane and Chris Savory. Code to identify defect species from input supercell structures was written based on the implementation in PyCDT by Broberg et al.

Contributing#

Bugs reports, feature requests and questions#

Please use the Issue Tracker to report bugs or request new features.

Contributions to extend this package are very welcome! Please use the “Fork and Pull” workflow to do so and follow the PEP8 style guidelines.

See the Contributing Documentation for detailed instructions.

Tests#

Unit tests are in the tests directory and can be run from the top directory using unittest. Automatic testing is run on the master and develop branches using Github Actions. Please run tests and add new tests for any new features whenever submitting pull requests.

License#

ShakeNBreak is made available under the MIT License.

Requirements#

ShakeNBreak is compatible with Python 3.8 & 3.9 and requires the following open-source python packages: