Powder Diffraction - Spallation Neutron Source

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$Single Crystal Diffraction - Spallation Neutron Source$

<strong>Diffraction</strong> from random polycrystalline material In a sufficiently large, randomly oriented polycrystalline sample (e.g. a powder) contains a very large number of crystallites. A beam impinging on the sample will find a representative number of crystallites in the right orientation for diffraction <strong>Diffraction</strong> occurs only at specific angles, those where Bragg’s Law is satisfied. Incident Beam Diffracted Beam 12
Bragg cones in powder diffraction Since there is a random distribution of crystals then diffraction occurs in all directions for each Bragg angle, 2, thus powder diffraction arises in cones Beam All reflections occurring at a single 2 value (as well as reflections at nearly the same value) are superimposed and only the sum of their intensities can be measured. For this reason a powder diffraction pattern gives less information than a single crystal measurement 13
Page 1 and 2: A Very Abbreviated Introduction to
Page 3 and 4: Where to go for more… There are m
Page 5 and 6: Basic Crystallography 5
Page 7 and 8: Lattice planes General Indices: la
Page 9 and 10: Diffraction from single crystals D
Page 11: Powder Diffraction 11
Page 15 and 16: Coherent Atomic Scattering Power (d
Page 18 and 19: Resonant Conditions X-rays X-ray fo
Page 20 and 21: Measuring powder diffraction Angul
Page 22 and 23: Highest resolution requires high co
Page 24 and 25: Powder Instruments: Constant Wavele
Page 26 and 27: Time of Flight Diffraction Time of
Page 28 and 29: Neutron Powder Diffraction with Spa
Page 30 and 31: Materials effects on Powder Diffrac
Page 32 and 33: Crystallite Size Broadening d*=cons
Page 34 and 35: Microstrain Broadening See GSAS Man
Page 36 and 37: Anisotropic strain broadening terms
Page 38 and 39: Fitting of Powder Diffraction Data
Page 40 and 41: Fitting crystallographic data -- wh
Page 42 and 43: Hugo Rietveld’s technique Hugo R
Page 44 and 45: Hugo Rietveld in the Petten Reactor
Page 46 and 47: Hugo Rietveld’s other breakthroug
Page 48 and 49: What sort of data are needed for Ri
Page 50 and 51: Limitations of Rietveld Rietveld c
Page 52 and 53: Approaches to Profile Models Three
Page 54 and 55: Voigt vs. Pseudo-Voigt A Gaussian c
Page 56 and 57: Axial Divergence (Low Angle Asymmet
Page 58 and 59: Sample Displacement & Transparency
Page 60 and 61: The Unit Cell The unit cell descri
Page 62 and 63:
Lattice Types Centering causes latt
Page 64 and 65:
Space Groups Not all combinations
Page 66:
Reciprocal Lattice To simplify mat
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Powder Diffraction - Spallation Neutron Source

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