Coupled reconstruction of adjacent polycrystalline grains from x-ray Bragg diffraction

Bragg coherent diffraction imaging (BCDI) provides nanometer-scale strain imaging of crystalline materials. In this project, we seek to study how atomic dislocations propagate across grain boundaries. However, established BCDI algorithms applied to different Bragg peaks of the same grain sample often reconstruct differing images, with the greatest uncertainty occurring around the edges of the grain. This makes it difficult to see how adjacent grains fit together and almost impossible to observe how they interact. We have demonstrated a novel BCDI algorithm which reconstructs several Bragg peaks in parallel, periodically bringing the amplitude and displacement fields of each of these reconstructions into agreement [1]. Here we will also report on an extension to this method to reconstruct adjacent grains simultaneously in order to better observe these dislocations near the grain boundary. We will show results on simulated reconstructions of adjacent grains and initial efforts at reconstructing twin grains in gold nanocrystals from the Advanced Photon Source beamline 34-ID-C.