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|Title:||Dr. Hans-Beat Buergi: Beyond Single Crystal Structure Determination - Disorder, Diffuse Scattering and Materials Properties|
|When:||04/ 1/2013 11:00 AM - 12:00 PM|
|Description:||Beyond Single Crystal Structure Determination -|
Disorder, Diffuse Scattering and Materials Properties.
Many materials owe whatever interesting properties they have to the fact that their crystal structures are disordered. Examples include alloys, high-Tc superconductors, thermoelectrics, light up-conversion materials and many more. With increasing degree of disorder structural models derived from Bragg diffraction tend to become physically or chemically untenable and insufficient to understand other experimental observations. The talk includes a very elementary introduction into the origin of diffuse scattering. Disordered crystals and their diffuse scattering are modeled with Monte Carlo calculations using the program ZODS (Zürich Oak Ridge Disorder Simulation). The model parameters are determined with genetic algorithms implemented on grid or parallel computers. Examples include a case with 1D diffuse scattering (streaks from stacking disorder) and its chemical background, a case with 2D diffuse scattering from an up-conversion material (diffuse planes due to coulomb-type frustration) and a case with 3D diffuse scattering from an SHG study.
Departement für Chemie und Biochemie, Universität Bern, and
Organisch-chemisches Institut, Universität Zürich