An algorithm for Bragg coherent X-ray diffractive imaging of highly strained nanocrystals

TL;DR

This paper introduces an advanced algorithm for Bragg Coherent Diffractive Imaging that successfully images highly strained nanocrystals and their phase transformations, overcoming limitations of previous methods in high-strain scenarios.

Contribution

The novel algorithm enables simultaneous reconstruction of multiple phase snapshots, allowing accurate imaging of highly strained nanocrystals during phase transformations.

Findings

Successfully reconstructs phase morphology with 1% strain difference.

Accurately images coexistent phases during structural transformations.

Enables operando visualization of phase changes in nanoparticle materials.

Abstract

By using phase retrieval, Bragg Coherent Diffractive Imaging (BCDI) allows tracking of three-dimensional displacement fields inside individual nanocrystals. Nevertheless, in the presence of significant (1% and higher) strains, such as in the process of a structural phase transformation, fails due to the Bragg peak distortions. Here we present an advanced BCDI algorithm enabling imaging three-dimensional strain fields in highly strained crystals. We test the algorithm on particles simulated to undergo a structural phase transformation. While the conventional algorithm fails in unambiguously reconstructing the phase morphology, our algorithm correctly retrieves the morphology of coexistent phases with a strain difference of 1%. The key novelty is the simultaneous reconstruction of multiple scans of the same nanoparticle at snapshots through the phase transformations. The algorithm enables visualizing phase transformations in nanoparticles of lithium-ion, sodium-ion nanoparticles, and other nanoparticulate materials in working conditions (operando).