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A physical optics formulation of Bloch waves and its application to 4D STEM, 3D ED and inelastic scattering simulations [software] Open Access

Bloch waves are often used in dynamical diffraction calculations, such as simulating electron diffraction intensities for crystal structure refinement. However, this approach relies on matrix diagonalisation, and is therefore computationally expensive for large unit cell crystals. Here Bloch wave theory is re-formulated using the physical optics concepts underpinning the multislice method. In particular, the multislice phase grating and propagator functions are expressed in matrix form using elements of the Bloch wave structure matrix. The specimen is divided into thin slices, and the evolution of the electron wavefunction through the specimen calculated using the Bloch phase grating and propagator matrices. By decoupling specimen scattering from free space propagation of the electron beam, many computationally demanding simulations, such as 4D STEM imaging modes, 3D ED precession and rotation electron diffraction, phonon and plasmon inelastic scattering are considerably simplified. The computational cost scales as O(N^2 ) per slice, compared to O(N^3 ) for a standard Bloch wave calculation, where N is the number of diffracted beams. For perfect crystals the performance can at times be better than multislice, since only the important Bragg reflections in the otherwise sparse diffraction plane are calculated. The physical optics formulation of Bloch waves is therefore an important step towards more routine dynamical diffraction simulation of large data sets.

Descriptions

Resource type

Software

Contributors

Creator: Mendis, Budhika ¹

¹ Durham University

Funder

Research methods

Other description

Code created using MATLAB.

Keyword

Bloch waves
Multislice
4D STEM simulations
Precession electron diffraction
Phonon scattering
Plasmon scattering

Subject

Bloch oscillations

Location

Language

Cited in

Identifier

ark:/32150/r2m613mx59t
doi:10.15128/r2m613mx59t

Rights

Creative Commons Attribution 4.0 International (CC BY)

Publisher

Durham University

Date Created

File Details

Depositor

B.G. Mendis

Date Uploaded

18 November 2024, 10:11:44

Date Modified

18 November 2024, 11:11:04

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File format: zip (ZIP Format)

Mime type: application/zip

File size: 36180

Last modified: 2024:11:18 10:41:53+00:00

Filename: Open Source Code.zip

Original checksum: d923e34382e279c3611f75cf87b08883