The influence of strain on image reconstruction in Bragg coherent X-ray diffraction imaging and ptychography

Abstract

A quantitative analysis of the effect of strain on phase retrieval in Bragg coherent X-ray diffraction imaging is reported. It is shown in reconstruction simulations that the phase maps of objects with strong step-like phase changes are more precisely retrieved than the corresponding modulus values. The simulations suggest that the reconstruction precision for both phase and modulus can be improved by employing a modulus homogenization (MH) constraint. This approach was tested on experimental data from a highly strained Fe–Al crystal which also features antiphase domain boundaries yielding characteristic π phase shifts of the (001) superlattice reflection. The impact of MH is significant and this study outlines a successful method towards imaging of strong phase objects using the next generation of coherent X-ray sources, including X-ray free-electron lasers.

Capturing Catalyst Strain Dynamics during Operando CO Oxidation

“…Previous BCDI studies have shown that the strain changes due to gas adsorption are localized at specific corners, edges, and facets, with density functional theory (DFT) studies showing the energies of adsorption differ for {111} and {110} facets. 12,15 For the shown nanoparticle, changes in strain are close to the top {111} facet during the CO condition, and across all facets during the reaction. Examples of the reconstructed particle strain are shown for each gas condition (dynamic and steady-state) in Figure 2c.…”

“…In order to probe the catalytically driven reaction, previous works have focused on the evolution of catalyst strain in well-faceted NPs. − In addition to facet-dependent catalytic activity, lattice strain is known to influence the reactivity of metal surfaces. A metal of particular interest, Pt, exhibits an increase (decrease) in the 5d-band energy by as much as 0.1 eV under a 1% tensile (compressive) strain .…”