Modelling dynamical 3D electron diffraction intensities. I. A scattering cluster algorithm

Area of Science:

• Crystallography
• Materials Science
• Electron Microscopy

Background:

• Three-dimensional electron diffraction (3D-ED) is crucial for characterizing nanoscale crystals unsuitable for X-ray diffraction.
• Accurate crystal structure refinement in 3D-ED requires dynamic treatment of Bragg diffracted intensities.
• Bloch wave simulations, while effective, are computationally intensive for crystals with large unit cells.

Purpose of the Study:

• To introduce and evaluate the scattering cluster algorithm (SCA) as a computationally efficient alternative to Bloch wave simulations in 3D-ED.
• To demonstrate the accuracy and speed of SCA for crystallographic characterization.

Main Methods:

• Developed the scattering cluster algorithm (SCA) by replacing eigen-decomposition with matrix multiplication.
• Applied SCA to model intensity transfer from neighboring beams to a specific Bragg reflection.
• Utilized a slice-based iterative calculation approach, similar to multislice methods, making SCA suitable for thin specimens.

Main Results:

• SCA provides a faster method for dynamic intensity treatment in 3D-ED compared to traditional Bloch wave simulations.
• The algorithm's accuracy and speed were validated using exemplar organic materials: tri-isopropyl silane (TIPS) pentacene and rubrene.
• Demonstrated the effectiveness of SCA for crystals with large unit cells.

Conclusions:

• The scattering cluster algorithm (SCA) is a viable and efficient computational method for 3D-ED analysis, especially for large unit cell materials.
• SCA offers a practical solution to the computational challenges posed by Bloch wave simulations in 3D-ED.
• This technique enhances the crystallographic characterization capabilities for nanoscale materials.