Powder Diffraction - Spallation Neutron Source

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$Single Crystal Diffraction - Spallation Neutron Source$

Lattice Types Centering causes lattice points to be placed inside units cells (body center, face centers) giving rise the 14 Bravais lattices (1848) { Have non-perpendicular axes: (non-orthogonal coordinate systems) (Figure from http://www.chemsoc.org/exemplarchem/entries/2003/bristol_cook/latticetypes.htm) 62
Symmetry The construction of a crystal from the unit cell requires repeated translation of the “building block” in all three directions: lattice symmetry § Additional symmetry is almost always present between the atoms in a unit cell. This means the unit cell (and thus the entire structure) can be built from just a section of the unit cell – The minimal section representative of the entire structure is called the asymmetric unit Types of symmetry elements in crystals – Lattice translations (includes lattice centering) – Mirror planes – Proper/improper Rotation axes (includes center of symmetry) – Screw Axes – Glide Planes (Images from http://members.tripod.com/~EppE/302rev2.htm) 63
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 and 12: Powder Diffraction 11
Page 13 and 14: Bragg cones in powder diffraction S
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 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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