Rietveld method/program

The catalysts were characterized by inductively coupled plasma emission spectroscopy (ICP-ES Perkin Elmer Optima 3300RL) to determine cobalt content, x-ray diffraction (XRD Bruker A-500) with crystallite size determination using the Rietveld method, and temperature-programmed reduction (Zeton Altamira AMI-200) using 30 ml/min 10% H2/Ar and a ramp rate of 10°C/min. Surface area... 

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... 

Izumi, F. (1993) Rietveld analysis program RIE-TAN and PREMOS and special applications. In Young, R.A. (ed.) The Rietveld Method, Oxford, Oxford University Press, 236-253 Jackson, B.P. Miller, W.P. (2000) Effectiveness of phosphate and hydroxide for desorption of arsenic and selenium species from iron oxides. Soil Sci. Soc. Am. J. 64 1616-1622 Jain, A. Raven, K.P. Loeppert, R.EI. (1999) Ar-senite and arsenate adsorption on ferrihy-drite Surface charge reductions and net OEI-release stoichiometry. Environ. Sci. Techn. 

It is worth noting that parameters identical to those listed in our examples can be expected only when the same computer codes are used to perform full profile refinement due to small but detectable differences in the implementation of the Rietveld method by various software developers. Furthermore, even when the same version of an identical computer program is employed to treat the same set of experimental data, small deviations may occur due to subjective decisions, such as when to terminate the refinement. In the latter case, however, the differences should be within a few least squares standard deviations. 

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... 

X-ray diffraction (XRD) patterns were measured at room temperature with a Siemens D-5000 Diffractometer that had a Cu Ka radiation. Intensity was measured by step scanning in the 20 range between 20 and 110° with a step of 0.02° and a measuring time of 2s per point. The DBWS-9600PC and WYRIET programs were used for crystalline structure refinements with the Rietveld method. From this refinement, the different phases and average crystalline... 

Full profile Rietveld method was used for the refinement of the lattice parameters, positional and displacement parameters of atoms. Data evaluation was performed by using the WrnCSD program package [5]. 

In seventies XRD methods gained still greater popularity as the Rietveld [223] program was introdueed. On the basis of the stmeture of all clinker phases the theoretical X-ray pattern can be ealculated, which then is eompared with the diffraction pattern of examined sample and correlated using the least square method. This method needs, however, the calibration curves determination for different clinker types, in order to take into aeeount the matrix influence. 

The Rietveld method is a refinement technique in which the whole powder pattern is fitted by varying a number of instrumental and stmctural-model parameters. The successful use of the method is directly related to the quality of both the diffraction data and the structural model being refined. The Rietveld method is widely available for the structure refinement of powder data through such programs such as GSAS, FullProf, and Rietan. ... 

Rietveld method, has been applied to describe chemical bonding, dynamic disorder, and anharmonic thermal vibration. Computer programs such as Rietan for the Rietveld analysis and PRIMA for the MEM analysis, which incorporate MEM and optimized for powder diffraction are available. 

Information content in a powder diffraction pattern is reduced as compared to that in single crystal diffraction, due to the collapse of the three dimensional reciprocal space into a one dimensional space where the only independent variable is the scattering angle. The poorer the resolution of the diffraction method, the less the information content in the pattern (Altomare et al. 1995 David 1999). As a consequence, structure of less complex phases can be determined from power diffraction alone (fewer atoms in the asymmetric unit of the unit cell). However, refinement of the structure is not limited so seriously with resolution issues, so powder diffraction data are used in Rietveld refinement more frequently than in structure determination. Electron powder diffraction patterns can be processed and refined using public domain computer programs. The first successful applications of electron diffraction in this field were demonstrated on fairly simple structures. 

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