Martin McBriarty: Top-Down Approaches to EXAFS Analysis

EXAFS spectra are often modeled using a small number of virtual coordination shells which can vary in coordination number, bond length, and disorder. While this bottom-up approach is generally successful for single-phase samples, it becomes intractable when the element of interest occupies multiple complex coordination states. Such cases may require a top-down approach, in which the measured spectrum is fitted using models with fixed atom positions and disorder. Given reasonable starting assumptions, such as ab initio molecular dynamics (AIMD) simulations of each possible component of the sample, the actual coordination states can be identified and quantified. I will present two examples of top-down solutions to difficult EXAFS problems: (1) the mechanisms of uranium incorporation into iron (oxyhydr)oxide minerals, and (2) the distribution of crystal phases in ferroelectric HfO2/ZrO2 nanostructures

https://onlinelibrary.wiley.com/doi/full/10.1002/pssb.201900285 https://pubs.acs.org/doi/abs/10.1021/acs.est.8b00297