PyExtal: a Python package for quantitative convergent-beam electron diffraction.

Area of Science:

• Materials Science
• Crystallography
• Computational Chemistry

Background:

• Quantitative Convergent-Beam Electron Diffraction (QCBED) is crucial for precise measurement of crystal structural parameters.
• Accurate QCBED relies on rigorous diffraction simulations and iterative intensity refinement.
• Existing methods can be limited in handling diverse crystal structures and data types.

Purpose of the Study:

• To introduce PyExtal, a novel Python-based software package for QCBED analysis.
• To provide automated computation workflows for refining small- and large-unit-cell crystals.
• To facilitate accurate electron charge density mapping and broader crystallographic applications.

Main Methods:

• Development of PyExtal, a Python software package utilizing dynamical diffraction theory.
• Implementation of automated computation workflows for QCBED data processing.
• Flexible data handling for both Convergent-Beam Electron Diffraction (CBED) and large-angle CBED patterns.

Main Results:

• PyExtal successfully refines structural parameters for benchmark systems like silicon and yttrium iron garnet.
• Refined silicon structure factors demonstrate excellent agreement with established experimental data.
• The software supports both small- and large-unit-cell crystal refinement.

Conclusions:

• PyExtal offers a robust and flexible computational platform for QCBED.
• The software enables accurate experimental mapping of electron charge density in crystals.
• PyExtal broadens the application scope of dynamical-diffraction-based quantitative crystallographic analysis.