Berlin 2008 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 6: Diffusion I

MM 6.2: Talk

Monday, February 25, 2008, 10:30–10:45, H 0111

Atomistic simulation of grazing incidence diffuse x-ray scattering from point defects — •Ruslan Kurta, Vladimir Bugaev, Melissa Delheusy, Andreas Stierle, and Helmut Dosch — Max-Planck-Institut für Metallforschung, Heisenbergstr.3, D-70569 Stuttgart, Germany

The investigation of defects in the vicinity of surfaces and interfaces is a current challenge, because such defects control important phenomena in the subsurface region, such as chemical reactions, ion conduction, performance of superconducting cavities. The challenge here is to understand microscopically the coupling of the defect-induced strain field to the interfaces. The goal of our project is the x-ray study and theoretical modeling of the strain field of point defects close to interfaces. Here, in particular, we present the results of an investigation of dissolved interstitial oxygen in the subsurface region of Nb (110), which plays a key role in the performance of high frequency cavities. The x-ray data were obtained from the diffuse x-ray scattering experiments under glancing-angle conditions. We use a semi-phenomenological Kanzaki-Krivoglaz approach to calculate the strain field around the point defect. For modeling of the diffuse x-ray scattering distribution in the vicinity of a surface we use a fully atomistic real-space ``large-sphere'' method. This allows one to obtain quantitative information about the defect distribution close to a surface. On the basis of the depth-resolved x-ray data we determined the subsurface concentration profile of the dissolved oxygen.