Refinement of the 200 structure factor for GaAs using parallel and convergent beam electron nanodiffraction data

Understanding crystal structure factors is essential for interpreting electron diffraction data. Prior research has shown that structure factors can be derived from isolated atom models, but these often neglect bonding effects. That uncertainty drove the development of new methods to refine structure factors using electron diffraction patterns. No prior work had resolved how to incorporate chemical bonding effects into structure factor calculations. Existing approaches rely on isolated atom models, which may not capture electron redistribution due to bonding. This gap motivated the need for a method that compares simulated and experimental diffraction intensities. Researchers have already demonstrated that electron diffraction can reveal crystal orientation and thickness. However, the influence of inelastic scattering on structure factor measurements remained unclear. This study aims to bridge the gap between isolated atom models and realistic bonding effects in electron diffraction.

The aim of this work is to refine the 200 structure factor for GaAs using electron diffraction data. The specific problem addressed is the influence of inelastic scattering and bonding effects on structure factor measurements. The motivation stems from the need to improve the accuracy of electron diffraction analysis in materials science. Current methods may not account for electron redistribution due to chemical bonding. This study proposes a new approach using Bloch wave refinement and simulated diffraction patterns. The researchers propose comparing calculated and experimental intensities to refine crystal parameters. The study also seeks to validate the method using two different experimental approaches. The goal is to determine whether structure factors derived from electron diffraction agree with density functional theory predictions.

The study uses Bloch wave refinement routines to compare simulated and experimental diffraction intensities. Calculated intensities are derived from frozen lattice and Bloch wave simulations. Experimental conditions are optimized using these simulations to guide data collection. The method is applied to GaAs diffraction patterns recorded under nearly parallel illumination. Two experimental approaches are used: unfiltered and zero loss filtered diffraction patterns. Structure factors are refined by adjusting crystal thickness, orientation, and atomic positions. Systematic errors are estimated by applying the method to simulated data. The results are compared to structure factors obtained from density functional theory calculations.

The 200 structure factor for GaAs was measured using two experimental methods. Both methods showed comparable precision and agreement with each other. The influence of inelastically scattered electrons was found to be negligible. Structure factors deviated by more than 20% from isolated atom model predictions. The results showed close agreement with density functional theory calculations. These calculations account for electron redistribution due to chemical bonding. The study confirmed that bonding effects significantly influence structure factors. The method successfully refined crystal thickness and orientation parameters.

The authors propose that their method effectively refines structure factors using electron diffraction data. They suggest that inelastic scattering has a negligible impact on structure factor measurements. The results suggest that bonding effects significantly influence structure factors. The authors propose that their method is suitable for personal computers due to low computational demand. They suggest that zero loss filtered and unfiltered diffraction patterns yield comparable results. The authors propose that density functional theory provides a better model than isolated atom assumptions. The authors suggest that their method improves the accuracy of electron diffraction analysis. The authors propose that this approach can be applied to other materials with similar crystal structures.