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Advanced Techniques in X-Ray Diffraction Analysis for Crystal Structure Determination

Learn about Laue, William Lawrence Bragg, crystal atomic arrangement, lattice in X-ray diffraction, wavelengths, experimental setups, monochromators, Bragg-Brentano geometry, diffractometers, powder/powdered samples, diffractograms, and fluorescence analysis.

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Advanced Techniques in X-Ray Diffraction Analysis for Crystal Structure Determination

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  1. MENA3100, 06/2-08, OBK X-ray diffraction, XRD (røntgendiffraksjon) Part 2 Laue William Lawrence Bragg 2dsinq = nl

  2. Crystal Atomic arrangement Lattice

  3. X-ray diffraction Need X-rays Wavelenght CuKa1 = 1.54056 Å MoKa1 = 0.70930 Å Characteristic X-rays CuKa1 = 1.54056 Å CuKa2 = 1.54433 Å Brehmsstrahlung = white radiation I(CuKa1) = 2·I(CuKa2) CuKa = 1.5418 Å

  4. Need sample Single crystal Powder

  5. Need experimental setup Bragg-Brentano geometry (Primary monochromator) Diffractometer (Secondary monochromator)

  6. Characteristic X-rays Brehmsstrahlung = white radiation Want monochromatic radiation Monochromators: Many possibilities

  7. Euclid, The Elements (300 B.C.) Proposition 21, Book III: The angles in the same segment of a circle are equal to another Johansson monochromator

  8. Bragg-Brentano geometry The source S can be:

  9. Need detector … Need some slits … Fixed slits: Smaler area at high angle  Smaller area at high angles Variable slits: Same area at all angles S Sample

  10. The experiment Got some crystals Want a powder Gets lot of small crystals

  11. Want powder Random orientation

  12. The result The diffractogram Quartz (Don’t call it spectrum)

  13. Why?

  14. Identification PDF = JCPDS

  15. Indexing

  16. Lattice dimensions

  17. Strain Particle size

  18. Fluorescens

  19. CuKa1 = 1.54056 Å CuKa2 = 1.54433 Å Primary and secondary monochromators

  20. Rietveld refinement

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