Computational Methods for Reconstruction of Nanoscale Strain Fields via Multi-Grain Bragg Coherent Diffraction Imaging

Bragg coherent diffraction imaging (BCDI) has the potential to provide significant insight into the structure-properties relationship for crystalline materials by imaging, with nanoscale resolution, three-dimensional (3D) strain fields within individual grains and nanoparticles. Recent methods for coupling reconstructions from several peaks to determine the full elastic strain tensor have been developed and applied to synthetic data, but have not been applied to experimental data. Using a coupled genetic reconstruction algorithm, this work presents reconstructions of an experimental data set and demonstrates improvements in the ability to resolve vector-valued displacement fields internal to the particle. For experimental data, reconstructions from the coupled Bragg peak algorithm show improvements over the non-coupled independent reconstruction method of 5% in terms of accuracy and 53% in terms of consistency. Additionally, this work presents the ability of this genetic algorithm to accurately reconstruct displacement fields about dislocations, showing a success rate of 90%. Finally, this work demonstrates a method for reconstructing neighboring grains simultaneously, improving the reconstructions by 13.5% in terms of reconstruction accuracy, and laying the foundation for polycrystal BCDI.