Neutron-related techniques | Least squares

Rietveld refinement

Rietveld refinement is a technique described by Hugo Rietveld for use in the characterisation of crystalline materials. The neutron and X-ray diffraction of powder samples results in a pattern characterised by reflections (peaks in intensity) at certain positions. The height, width and position of these reflections can be used to determine many aspects of the material's structure. The Rietveld method uses a least squares approach to refine a theoretical line profile until itmatches the measured profile. The introduction of this technique was a significant step forward in thediffraction analysis of powder samples as, unlike other techniques at that time, it was able to deal reliably with strongly overlapping reflections. The method was first implemented in 1967, and reported in 1969 for the diffraction of monochromatic neutrons where the reflection-position is reported in terms of the Bragg angle, 2θ. This terminology will be used here although the technique isequally applicable to alternative scales such as x-ray energy or neutron time-of-flight. The only wavelength and technique independent scale is in reciprocal space units or momentum transfer Q, which is historically rarely used in powder diffraction but very common in all other diffraction and optics techniques. The relation is (Wikipedia).

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pyGSAS (GSAS-2) Rietveld Refinement intro tutorial

brief introduction to using free GSAS-II (pygsas) software to do rietveld refinement. For those interested in following along, sample files can be found through this link https://drive.google.com/drive/folders/17ywJW366y3iWpna3tWDzrpEEuFs-SRVv?usp=sharing or emailed upon request if that's

From playlist Software tutorials

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From playlist The 2nd Asia Pacific Workshop on Quantum Magnetism

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From playlist Transformations

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GSAS-II export to XRD plot

Tutorial showing how to export a Rietveld refinement from GSAS-II (pyGSAS) into QTGrace in order to make nice plots.

From playlist Software tutorials

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From playlist Hacking at Random (HAR) 2009

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From playlist Transformations

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The Riemann Hypothesis

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From playlist And 1, and 2, and 1,2,4,1!

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From playlist RubyConf 2015

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From playlist Integrals

Related pages

Momentum transfer | Powder diffraction | Multiplicity (mathematics) | Bragg's law | Least squares | Neutron diffraction