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An algorithm for calculating the 2θ diffraction profiles is developed based on the dynamical theory of X-ray diffraction for multi-beam cases. The connection between the 2θ-scanned profiles and the excitation of modes is revealed.

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Acta Cryst. (2014). A70, C391
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We have used resonant multi-beam diffraction with the primary reflections G=(h/2 h/2 0) and G=(h/4 h/4 0) (h is an odd number) to investigate the charge ordering and Jahn-Teller distortion, respectively, in La0.5Sr1.5MnO4 low temperature phase. While the Renninger scans with G=(h/2 h/2 0) shows several Aulfhellung-type four-beam diffraction, most of the multi-beam diffraction with G=(h/4 h/4 0) has an Umweganregung-type nature. A detailed study of multi-beam diffraction anomalous fine structure (M-DAFS) of (0 0 0)/(3/2 3/2 0)/(1 -1 0)/(5/2 1/2 0) OUT diffraction is carried out. Its triplet invariant phase approach 1800 when the x-ray energy is tuned away from manganese K-edge, and approach 900 when the x-ray energy is tuned on manganese K-edge. In other words, its multi-beam diffraction profile shows strong asymmetry when (3/2 3/2 0) diffraction intensity is dominated by Jahn-Teller distortion, and becomes more symmetric when charge ordering dominated. This characteristic can be successfully simulated by tensor form dynamical x-ray diffraction theory accompanied with FDMNES software [1] calculations.

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Acta Cryst. (2014). A70, C1740
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With rapid advances in the international scientific community as well as increasing demands for bright X-rays from users to facilitate their challenging scientific experiments, the construction of a new synchrotron facility was vital to maintaining National Synchrotron Radiation Research Center in Taiwan to be globally competitive. After conducting numerous assessments with our users, the decision to construct Taiwan Photon Source (TPS) was made at the meeting of Board of Trustee held in 2004 July. This large-scale project will establish, at the current campus of NSRRC, a new, low-emittance, synchrotron light source of circumference 518 m and with an electron beam of energy 3 GeV. TPS is designed to emphasize electron beams of small emittance and great brilliance for generating extremely bright photon beams. The superior characteristics of TPS have opened avenues for novel scientific opportunities and experimental techniques. The advanced techniques of phase-I beamlines include temporally coherent X-ray diffraction, protein microcrystollography, submicron soft X-ray spectroscopy, coherent X-ray scattering, submicron X-ray diffraction, X-ray nanoprobe, and high resolution inelastic soft X-ray scattering. Taking full advantage of the highly brilliant photon source, the seven planned beamline will aim for the forefront of science. These beamlines cover diverse research in physics, chemistry, biology, and material science, in the energy range from soft to hard X-rays for advanced research in spectroscopy, scattering and imaging.

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Acta Cryst. (2014). A70, C1781
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Local structures surrounding Co dopoant atoms in (Y,Co) codoped CeO2 nanocrystals prepared by a chemical method followed by a series of thermal annealing and x-ray exposure have been probed using x-ray absorption fine structure (XAFS) techniques. These material systems are of great interest for catalytic applications. Our x-ray results show systematic variation of local structures surrounding Co atoms due to thermal annealing at different temperatures. It was also found that x-ray exposure with sufficient incident photon energy can substantially neutralize the structural effects of annealing. A theoretical model based on calculation using the Vienna ab initio Simulation Package (VASP) was proposed to identify relevant dopant locations that lead to the observed XAFS results and to explain the migration of Co in the CeO2 host due to the x-ray and thermal treatments. Manipulation of dopant atoms using x-ray exposure may provide unprecedented opportunities for tuning the physical properties of these materials for catalytic applications.
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