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Multimodal approaches to determining atomic order on the nanoscale

Abstract

Functional properties of materials frequently depend on details of atomic order on the scale ranging from sub-nanometer to several nanometers, where traditional crystallographic methods of structure determination relying on Bragg diffraction become ineffective.   X-ray/neutron total-scattering, which combines Bragg peaks with diffuse scattering reflecting local interatomic correlations, gains popularity as a tool for determining the local structure in complex materials.  However, obtaining fully atomistic models from such data alone is an underdetermined problem.  We have addressed this challenge by developing a structure-refinement framework that integrates several types of diffraction and spectroscopic data to obtain structural models that capture atomic arrangements over length scales up to 10 nm.  We will illustrate the capabilities of this method with structural refinements in perovskite-like ferroelectrics using simultaneous fitting of 3D X-ray single-crystal diffuse scattering and X-ray & neutron total-scattering datasets measured on the powder version of the same material.  We will also share our recent explorations of structural refinements for biomolecules in solutions from combined small- and wide-angle X-ray scattering data.

Biography

Igor Levin leads the Materials Structure & Data Group at the National Institute of Standards and Technology in Gaithersburg, MD (https://www.nist.gov/mml/materials-measurement-science-division/materials-structure-and-data-group).  He received his Dipl. Eng. in Metallurgy (with distinction) from the Polytechnical Institute in St. Petersburg, Russia, and both M. Sc. & D. Sc. Degrees (advised by Prof. David Brandon) in Materials Science from the Technion – Israel Institute of Technology. Dr. Levin is pursuing research into structure-property relationships in functional materials by developing methods for combining inputs from diffraction, spectroscopic, and transmission electron microscopy techniques to obtain structural models that span length-scales from sub-nanometer to macroscopic. His recent interests also include ceramic processing and additive manufacturing.