Science’s conception of the atomic-scale structure of crystalline materials derives from the Bragg peaks in X-ray diffraction and their obligatory origin in the periodic crystal lattice. But if Bragg had had access to synchrotron radiation and its associated local structure methods we would view materials quite differently. Although periodicity has been infinitely useful in understanding the properties of matter, it is also quite limiting in that almost all materials of technological and scientific interest contain impurities or other defects in their crystal structures, sometimes inadvertent or as the consequence of aging but just as often deliberately introduced, that determine their behaviors and utility. Since these break the periodicity and symmetry their signatures in crystallography are often small and ambiguous and conventional refinement methods give results that can be removed from reality. Elucidating structure: function relationships - in complex structural materials, electronic and correlated materials, catalysts, and even environmental and forensic samples - therefore requires complete structure determination that includes complementary crystallography that determines the long-range average structure of the periodic portion of the material and local structure methods, e.g., XAFS and pair distribution function analysis, that are sensitive to local order. Other methods can also be essential, e.g., microscopy that reveals unexpected interactions and “chemistry” between separate phases. In addition, these x-ray techniques also provide information on dynamical aspects of the structure via their inelastic or instantaneous methods that are complementary to elastic and inelastic neutron scattering. The missing idea that necessitates this range of experimental measurements is strong interactions, i.e., collective and cooperative behavior, between these “defects” or inhomogeneities that can cause them to cluster or self organize in other ways, especially in non-equilibrium systems.
Organizer:
Steven Conradson, Jozef Stefan Institute & Washington State University
Session Moderators:
Alan Bishop, Los Alamos National Laboratory, New Mexico
Jose Mustre, Director General, Cinvestav, Mexico
Agenda:
7:30 AM Steven Conradson; Jozef Stefan Institute & Washington State University: Interacting Defects and Differently Ordered Materials
8:00 AM Akhil Tayal; Deutsches Elektronen-Synchrotron DESY: Effect of Interfacial Structure on Catalytic Properties of Bimetallic Nanoparticles
8:30 AM Takeshi Egami; Institute for Neutron Sciences, Oak Ridge National Laboratory & University of Tennessee: Probing Local Dynamics in Disordered Systems
9:00 AM Andrea Perali; Camerino University & Marcello Barbosa da Silva; Universidade Federal do Rio de Janeiro: Dynamic Structure and its Ramifications in Cuprates
9:30 AM Stuart Parkin; Max Planck Institute of Microstructure Physics: Unusual electron orders: Weyl semi-metals, Heusler alloys, and anti-skyrmions
10:00 AM Dragan Mihailovic; Jozef Stefan Insitute: Hidden Orders Revealed by Ultrafast Spectroscopy
10:30 AM Nicola Poccia; Leibniz Institute for Solid State and Materials Research Dresden: Aggregation on Multiple Length Scales in Complex Materials
11:00 AM Yanwen Sun; SLAC National Accelerator Laboratory/LCLS: Probing nano/atomic scale fluctuations with speckle visibility spectroscopy
11:30 AM Panel discussion: Differently ordered materials, including questions and comments from audience
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