<i>EDINP</i>, the Edinburgh powder profile refinement program

Pawley, G. S.

doi:10.1107/s0021889880012964

Cited by 102 publications

(83 citation statements)

References 5 publications

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“…The experimental powder diffraction profiles were analysed by means of the program EDINP (Pawley, 1980). In this modification of the Rietveld profile analysis program (Rietveld, 1969) the molecular orientation and the C-S bond length can be constrained during the initial cycles of refinement.…”

Section: Discussionmentioning

confidence: 99%

Structure of solid carbon disulphide between 5 and 150 K

Powell¹,

Dolling²,

Torrie³

1982

Acta Crystallogr Sect B

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The crystal structure of CS2 has been determined at six temperatures from 5.3 to 150 K using the neutron powder profile refinement technique. The results confirm the general features of the structure determined earlier at high temperatures. The space group is Cmca at all temperatures with four molecules per unit cell, and the lattice parameter, c, decreases as the temperature increases. Specific parameters of the structure differ from the earlier determination, and the C-S bond length in the solid appears to be shorter than in the gas phase. At 5.3 K the bond length is 1.546 (2) A and the lattice parameters are a = 6.0864 (3), b = 5.2866 (3) and c= 9.4623 (5)/k. At 150 K the corresponding values are 1.529(4), 6.4141 (7), 5.5787(7) and 8-8928 (11) A.

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Section: Discussionmentioning

confidence: 99%

Structure of solid carbon disulphide between 5 and 150 K

Powell¹,

Dolling²,

Torrie³

1982

Acta Crystallogr Sect B

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“…A plethora of Rietveld-analysis computer programs has arisen apace with this dramatic increase in popularity of the method, as individual research groups either modified already established and widely circulated programs, such as those of Hewat (1973) and Wiles & Young (1981) or wrote new code from scratch (for example, Pawley, 1980;Von Dreele, Jorgensen & Windsor, 1982;Baerlocher, 1982;Izumi, 1985).…”

Section: Introductionmentioning

confidence: 99%

Rietveld refinement round robin. I. Analysis of standard X-ray and neutron data for PbSO₄

Hill¹

1992

J Appl Cryst

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The Commission on Powder Diffraction of the International Union of Crystallography has undertaken an intercomparison of Rietveld refinements performed with two 'standard' PbSO4 powder diffraction patterns: a conventional (two-wavelength) X-ray pattern collected on a Bragg-Brentano diffractometer with Cu Ks radiation and a constant-wavelength neutron pattern collected on the D1A diffractometer at the Institut Laue-Langevin. The aims of this project were: (i) to evaluate a cross section of currently used Rietveld refinement software; (ii) to examine the range and effect of various strategies of Rietveld refinement; (iii) to assess the precision and accuracy (spread) of the parameters derived by Rietveld analysis. 23 participants provided 18 refinements with the X-ray data and 20 refinements with the neutron data, using 11 different Rietveld-analysis programs. Analysis of the submitted results shows that refinement strategies play a large part in determining the detailed outcome of a Rietveld refinement. The wide variation in the values of the agreement indices obtained in these studies of the same data sets highlights the need for standardization both of the refinement procedures and of the type of data included tn the algorithms used for assessing the fit. The major factors limiting the accuracy of the derived PbSO4 crystal structure parameters were: (i) use of insufficiently flexible peak shape and/or background functions; (ii) elimination of the high-angle diffraction data from the refinement; (iii) inclusion of an insufficiently wide range of diffraction angles on either side of the centroid of each peak during the step intensity calculation; and, additionally for X-rays, (iv) simultaneous release of the O-atom site-occupancy and displacement parameters. Rietveld analysis of the PbSO4 X-ray powder diffraction data provided atomic coordinates and isotropic displacement parameters for the Pb and S atoms that are precise (i.e. have small e.s.d.s) and are in reasonable agreement with the values derived from a singlecrystal study (viz the spread of coordinates is over the range 0.007-0.042 A). On the other hand, the 'light' 0021-8898/92//050589-22506. 00 O-atom parameters show relatively poor precision and have a disconcertingly wide spread of values about the weighted mean (viz 0.12-0.19A for the coordinates). Despite the much lower intrinsic resolution of the neutron data (i.e. peak widths some four times those of the X-ray data), the coordinates and anisotropic displacement parameters obtained for the Pb and O atoms are very precise and have a relatively narrow distribution about the single-crystal results, namely 0.004-0.020 A for the coordinates. The range of coordinates determined from the neutron data for the relatively 'light' S atom is correspondingly larger, namely 0.024-0.043 A, about equivalent to that obtained from the X-ray data. In general, and as expected, the e.s.d.s from the Rietveld analyses are substantially smaller than the observed inter-refinement variation of the unit-cell dimensions...

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“…Thus, supplementary information is needed for a sufficiently good refinement of a crystal structure. Usually, it comes from: (a) elimination of some of the parameters as independent variables by constraining them to be functions of others (Immirzi, 1980;Pawley, 1980); (b) introduction of restraints on some geometric or energy parameters (Baerlocher, 1993;Elsenhans, 1990;Izumi, 1989); (c) the integration of an X-ray diffraction pattern with a neutron pattern. Such a practice is suggested by fact that X-rays and neutrons are scattered by different mechanisms (Larson & Von Dreele, 1987).…”

Section: Amount Of Information In a Powder Diagrammentioning

confidence: 99%

Direct Methods and Powder Data: State of the Art and Perspectives

Giacovazzo¹

1996

Acta Cryst Sect A

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Solving crystal structures by applying direct methods to single-crystal data is a relatively easy task for structures with up to 100 atoms in the asymmetric unit. Their successful application to powder data is still a challenge unless the size of the structure is moderate. The rate of success depends on several factors like the efficiency of the full-pattern-decomposition programs, the peak overlapping, the presence of preferred orientation in the powder specimen, the nature of the background, the type of radiation used for collecting experimental data etc. The main factors are analysed in order to provide a clear description of the specific problems that have to be forced when direct phasing from powder data is attempted.

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EDINP, the Edinburgh powder profile refinement program

Cited by 102 publications

References 5 publications

Structure of solid carbon disulphide between 5 and 150 K

Structure of solid carbon disulphide between 5 and 150 K

Rietveld refinement round robin. I. Analysis of standard X-ray and neutron data for PbSO₄

Direct Methods and Powder Data: State of the Art and Perspectives

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EDINP, the Edinburgh powder profile refinement program

Cited by 102 publications

References 5 publications

Structure of solid carbon disulphide between 5 and 150 K

Structure of solid carbon disulphide between 5 and 150 K

Rietveld refinement round robin. I. Analysis of standard X-ray and neutron data for PbSO4

Direct Methods and Powder Data: State of the Art and Perspectives

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Product

Resources

About

Rietveld refinement round robin. I. Analysis of standard X-ray and neutron data for PbSO₄