orgdisord#

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Python code to handle disordered molecular crystals.

Warning

This is a work in progress. The code is not yet ready for general use.

Features#

  • Parse CIF files marked up with disorder.

  • Enumerate all possible ordered configurations from a disordered CIF file, given a supercell size.

  • Merge symmetry equivalent ordered configurations using a variety of strategies:

    • Using symmetry operations defined in the CIF file

    • Computing and comparing Ewald energies

    • Computing a SOAP descriptor and comparing using the REMatch kernel

  • Visualise the merged configurations using ASE, with different disorder assemblies/group tagged.

  • Output the generated (merged) configurations in a number of formats (cif, xyz, poscar, cell).

Limitations#

  • Disorder in the CIF file must be marked up using the _atom_site_disorder_group and _atom_site_disorder_assembly tags.

  • The handling of Z’ < 1 is not currently robust and will not work in many cases. In addition, the generation of supercells in Z’ < 1 cases currently generates structures with overlapping atoms.

Quick start examples#

The examples below assume you have installed the package as per the Installation instructions and have the example CIF file in the current directory. You can download the example CIF file here: ABABUB.cif

  1. Generate all possible ordered configurations in the primitive cell:

    $ orgdisord enumerate ABABUB.cif --no_write --view

  2. Generate all possible ordered configurations in a 2x1x1 supercell:

    $ orgdisord enumerate ABABUB.cif --supercell 2 1 1 --no_write --view

  3. Merge fully enumerated configurations:

    $ orgdisord enumerate ABABUB.cif -m --no_write --view

  4. Merge randomly generated configurations in the primitive cell. If you have enough of them, you will end up with the same groups as the fully enumerated case (though this is much less efficient):

    $ orgdisord enumerate ABABUB.cif -m --no_write --view --random -N 1000

  5. Generate 5000 randomly ordered structures in a specified supercell:

    $ orgdisord enumerate ABABUB.cif --supercell 2 1 2 --random -N 5000 --no_write --view

  6. Generate 3 randomly ordered structures in a very large supercell:

    $ orgdisord enumerate ABABUB.cif --supercell 4 6 4 --random -N 3 --no_write --view

Notice that a orgdisord.log file is generated in the current directory. This file contains the full command line options used to generate the output, as well as information about how the CIF file was parsed, the enumeration was done and, if applicable, how the merging was done. This can be useful for debugging and reproducing results.

The command line interface documentation has full details of the available commands and options. Alternatively you can run orgdisord --help to see the available commands and e.g. orgdisord enumerate --help to see the available options for the enumerate command.

Note

For each of these examples we included the --no_write option to prevent the configurations from being written to file. Without this flag, the code will write the configurations, in extended xyz format, into a directory named orgdisord-results, and it will also generate a .csv file containing a summary of the generated structures.

We also included the --view option to visualise the merged configurations using ASE. In the ASE GUI, you can click View→Colors and select color By Tag to easily see the different disorder assemblies and groups. You can also click View→Show Tags to see the tags associated with each atom.

For more examples and case studies, see the Case Studies page.