ciffetch

ciffetch is a PyQt6 dialog for searching the Crystallography Open Database (COD) and retrieving crystal structure data as CIF files. It can be run as a standalone application or embedded in another PyQt application.

Search using chemical formula or required elements, space group, lattice parameter ranges, text, journal, and publication year. Matching entries appear in a sortable results table; double-click an entry to choose where to save its CIF file.

Requirements

• Python 3
• PyQt6
• requests

Install the dependencies with:

python -m pip install PyQt6 requests

Run the application

python ciffetch.py

Enter search criteria in the dialog and run the search. Double-click a result to fetch its CIF file and save it to a chosen location.

Use from a PyQt application

Create a QApplication, instantiate CifFetchDialog, and call fetch_cifs(). The sigFileFetched signal provides the saved file path and CIF text when a file has been fetched:

import sys

from PyQt6.QtWidgets import QApplication
from ciffetch import CifFetchDialog

app = QApplication(sys.argv)
dialog = CifFetchDialog()
dialog.sigFileFetched.connect(
    lambda path, cif_content: print(f"Saved {path} ({len(cif_content)} characters)")
)
dialog.fetch_cifs()
sys.exit(app.exec())

For single-file selection, call dialog.fetch_single_cif() instead. CifFetchDialog also emits the standard accepted() signal after a file is fetched in single-file mode. The get_latest_saved_file() method returns the most recently saved file path.

Acknowledgment and data

This application is made possible by the people behind the Crystallography Open Database. COD data and the database are dedicated to the public domain under CC0. Users of COD data should acknowledge the original authors of the structural data and cite the relevant source information provided with each entry.

License

The ciffetch software is licensed under the GNU General Public License, version 3. This software license is separate from the license and attribution requirements for data retrieved from COD.