Neutron Rietveld method

In a paper by Albinati and Willis (1982) the application of the Rietveld method in neutron and X-ray powder diffraction was discussed considering the different experimental techniques of obtaining the diffraction patterns. For a detailed description of the method and its applications see a reference publication (Young 1995). See also Jenkins and Snyder (1996). A frequently used calculation program for the... 

During the last five years, a powerful new method of getting crystal structural information from powder diffraction patterns has become widely used. Known variously as the Rietveld method, profile refinement1, or, more descriptively, whole-pattern-fitting structure refinement, the method was first introduced by Rietveld (X, 2) for use with neutron powder diffraction patterns. It has now been successfully used with neutron data to determine crystal structural details of more than 200 different materials in polycrystalline powder form. Later modified to work with x-ray powder patterns (3, X) the method has now been used for the refinement of more than 30 crystal structures, in 15 space groups, from x-ray powder data. Neutron applications have been reviewed by Cheetham and Taylor (5) and those for x-ray by Young (6). 

Peplinski B, Schultze D, Wenzel J (2001) Interlaboratory comparison (round robin) on the application of the Rietveld method to quantitative phase analysis by X-ray and neutron diffraction. In Delhez R, Mittemeijer EJ (eds) Proc 7th European powder diffraction conference (EPDIC-7), Barcelona, Spain, 20th 23rd May 2000, Trans Tech Publications Ltd, Switzerland, p 124... 

A complete understanding of the structure of the material under study or application is a sine qua non condition for the successful research or use of the material. In the case of powders, the best way to decipher the structure of new materials is the Rietveld method. This methodology was initially developed by Hugo M. Rietveld in 1969 [23] as a procedure for refining crystal structures using neutron powder diffraction data. To implement the method in practice, certain information about the estimated crystal structure of the phase or phases of interest in the diffraction profile under test is necessary. 

Hill, R. J., and Howard, C. J. Quantitative ph2ise analysis from neutron powder diffraction data using the Rietveld method. J. Appl. Cryst. 20, 467-474 (1987). Franklin, R. E., and Gosling, R. G. Molecular configuration in sodium thymonu-cleate. Nature (London) 171, 740-741 (1953). 

The traditional method to measure the pole distributions becomes unsatisfactory if the peaks are overlapped. This happens for low symmetry compounds or when the sample contains many phases. In addition, by using a position sensitive detector or neutron time-of-flight diffraction, a large segment or the whole pattern can be recorded simultaneously, and using only a small number of peaks, a large volume of information is lost. To eliminate these drawbacks, Wenk, Matthies and Lutterotti proposed a combination of the WIMV procedure (or other inversion method) with the Rietveld method - more exactly with the Le Bail (Chapter 8) routine for peak intensity extraction. In this combined method it is presumed that the structural parameters, or... 

Later Von Dreele implemented the general description of texture by spherical harmonics in GSAS. Von Dreele proved that, by using this description, beside the robustness of the texture correction in the Rietveld method it is also possible to perform a reliable quantitative texture analysis. He measured by neutron time-of-flight diffraction a standard calcite sample previously used for a texture round robin. The patterns from different detector banks and sample orientations were processed by GSAS, refining the harmonic coefficients simultaneously with the structural and other parameters. Six pole distributions calculated from the refined harmonic coefficients and used as input in the... 

C. Rietveld performs crystal structure refinement and quantitative phase analysis using powder diffraction data and the Rietveld method. Combining refinement programs and advanced modeling tools allows a faster route to determining the structures of both inorganic and molecular crystals. An effective way to know the atomic structure is by means of diffraction techniques using neutrons from nuclear reactors and particle accelerators or X-rays from... 

In this chapter diffraction and in particular X-ray and neutron diffraction will be described in general, with an emphasis on powder diffraction techniques. The specific properties of X-ray and neutron diffraction and a description of sources and instruments for powder diffraction studies will be presented. Furthermore the use of powder diffraction data, from the simple use for phase identification to structure solution and refinements with the Rietveld methods, will be described. Two examples showing the potential for powder... 

Neutron upper part) and X-ray lower part) powder diffraction spectra of maghemite. The two patterns were simultaneously refined by the Rietveld method (the difference between model and measurement can be seen as the bottom curves of both parts). The arrows (In both parts) indicate extra reflections, due to tetrahedral ordering of vacancies In the crystal... 

Wright AC (1994) In Baruchel J, Hodeau JL, Lehmann MS, Regnard JR, Schlenker C (eds) Neutron and synchrotron Radiation for condensed matter studies, vol II, Chap VIII. Springer, Berlin, pp 167-196 Young RA (1993) The Rietveld method. Oxford University Press, Oxford... 

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