Theme I: Instrument and Method Development | Argonne National Laboratory

We are strongly involved in the ongoing development of novel instrumentation, techniques, and data analysis tools that advance our scientific programs and enable new science.

The group plays an active and important role in expanding the capabilities of existing instrumentation and in developing novel instrumentation and methods, which enable our studies of complex ionic, spin, chargen and lattice correlations and their relation to emergent phenomena.

Single Crystal Diffuse Scattering

Our group led the development of novel single crystal diffuse neutron and synchrotron X-ray scattering techniques, which have the potential for broad impact in determining the relations between local correlations on the nano- and mesoscale and emergent physical phenomena. These efforts recently led to the development and funding of the Corelli single crystal diffuse scattering instrument at the Spallation Neutron Source at Oak Ridge National Laboratory (https://neutrons.ornl.gov/corelli).

Illustration of the workflow to determine complex disordered structures by utilizing high intensity neutron or synchrotron x-ray beams in combination with fast area detectors and efficient software to transform and analyze large datasets.

3D-ΔPDF Analysis

The availability of scattering intensities from single crystals over large volumes of momentum transfer enables transformation into three-dimensional pair-distribution functions (3D-PDF) via Fourier transforms. By subtraction the Bragg peak intensities from the observed Data before performing the transforms, we obtain the 3D-ΔPDF, which is the probability of a two-particle pair vector with respect to the average structure.

The 3D-ΔPDF transform of measured diffuse scattering (left) from crystalline sample with complex disorder contains negative (blue) and positive (red) intensities that denote interatomic vectors that are less (blue) or more (red) likely to occur in the disordered than average structure.

Polarized Neutron Reflectometry

A test demonstrates the ability to measure two samples simultaneously, which allows more efficient use of the beam or measurement of a reference with the sample.

Polarized Neutron Reflectometry (PNR) is a well-established technique that uniquely provides chemical and magnetic depth profiles. We are further developing this technique in order to make more efficient use of the neutron beam and to improve the accuracy of reflectivity curves measured over large ranges of momentum transfer.