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Comprehensive Overview of EVAL-14 Data Reduction and Peak Search Techniques

EVAL-14 is a sophisticated software for data reduction in crystallography, developed and maintained by esteemed researchers at Utrecht University. It utilizes advanced peak search and cell determination through Dirax, along with generating “shoebox” files for integration with eval. The process includes cell refinement and allows repeated iterations until optimal results are achieved. Data can be exported as CIF or SHELX-style HKL files. Despite its computational intensity and complex parameter tuning, EVAL-14 is capable of handling anisotropic mosaic patterns and challenging reflections, making it a valuable tool in crystal analysis.

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Comprehensive Overview of EVAL-14 Data Reduction and Peak Search Techniques

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Presentation Transcript

  1. EVAL-14: Use at RESI

  2. Data reduction process at RESI • Peaksearch and cell determination with Dirax • Generation of “shoebox”-files • Integration with eval • Cell refinement • Repeat from 2 until satisfied • Data export as cif or shelx-style hkl-file

  3. Basics of EVAL-14 • Developed and maintained by Albert J. M. Duisenberg, Loes M. J. Kroon-Batenburg and Antoine M. M. Schreurs (Utrecht University), distributed by Bruker. • Albert J. M. Duisenberg et al. Intensity evaluation method J. Appl. Cryst. (2003). 36, 220-229 • Prediction of peak position and shape by ray-tracing.

  4. Factors influencing the peak shape • The source: Size, Divergence and wavelength distribution • The sample: Mosaic, crystal shape+aligment

  5. Source description • Rectangular shape at fixed distance • For neutron case: fixed single wavelength • (x-ray: α1/ α2)

  6. Crystal description • Sphere with radius r or • Rectangular block enclosing the actual shape • Mosaic spread • Possibly anisotropic moasic

  7. Generating the profile • Simplification of the 3-D profile by only looking at the projections along w, XD,YD • Contours generated by sub-profile addition

  8. The integrated intensity • Preduction to “shoeboxes” • With the final contour: Background-Peak-Background (BPB) integration • For strong reflections shifting of the final peak position

  9. Advantages • Works in the absence of strong “model reflections” • Can model anisotropic mosaic or diffuse streaking • Works in the presence of “alien” reflections (e.g. twins, other phases, multigrain crystals) • Many parameters to tune

  10. Disadvantages • Quite computing intensive • Many parameters to tune • Commercial software

  11. Detector image

  12. ”Shoeboxes” in the integration view

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