Matches in SemOpenAlex for { <https://semopenalex.org/work/W2329799294> ?p ?o ?g. }
- W2329799294 endingPage "162" @default.
- W2329799294 startingPage "146" @default.
- W2329799294 abstract "Abstract In the Rietveld method for the analysis of powder diffraction data the entire pattern is calculated using a model for the positions of the peaks (the unit cell parameters), their intensities (dependent on the atomic positional and thermal parameters, preferred orientation, etc.) and their widths and shapes, together with a description of the background. The calculated pattern is then compared with the observed step profile, point by point, and the model parameters are adjusted by least-squares methods. In order to ensure the best possible outcome of the refinement, a number of critical decisions must be made prior to the collection of the step intensities. For constant wavelength diffractometers, these decisions relate to the wavelength, beam collimation, range of diffraction angles, angular distance between steps, and counting time (X-rays) or monitor setting (neutrons) at each step. The effect of the first three of these factors is well known, but the selection of appropriate values for the counting time T (in effect, the intensity) and for the step interval (which, for a given scan range, determines the number of steps, N) is not straightforward. In fact, N and T are usually chosen more by tradition or by pressure of instrument time than by a consideration of their possible effect on the results of the analysis. Since each measured step intensity is used in the Rietveld method, the number of ‘observations’, N, in a scan can be made arbitrarily large (independent of the number of Bragg reflections) by decreasing the step interval. It is, however, the intensities of the Bragg peaks that are the fundamental quantities in any structure analysis, not the step intensities themselves. Thus, although the precision of the peak intensity measurement is improved by increasing N or T, this only occurs up to the point where counting variance becomes negligible in relation to other sources of error; further increases provide no additional structural information. Systematic studies of the effect of variations in T indicate that the optimum value of the maximum step intensity is only a few thousand counts. If significantly larger numbers of counts are accumulated, the accuracy of the structural parameters is not improved, time is wasted, and the usual weighting scheme based on counting variance becomes inappropriate (i.e., the parameter esd's reflect their precision rather than their accuracy). In the case of step width, the optimum value is between one-fifth and one-half the minimum full-width at half-maximum (FWHM) of well-resolved peaks, the exact value depending on T and the complexity of the diffraction pattern. Smaller steps provide little or no improvement in parameter accuracy (especially when step intensities are large) and, at the same time, introduce serial correlation between adjacent residuals in the profile, again leading to wasted time and corruption of the esd's. In practice, it is the combination of N and T chosen for the experiment that is of greatest importance in determining the efficiency of the data collection strategy. If the pattern has many overlapping peaks, N should be large, corresponding to a step interval of about FWHM/5, to provide adequate peak resolution, and T should be correspondingly small to minimize serial correlation. For a fixed total data collection time, a given level of Rietveld precision can be achieved more efficiently by the use of large N and small T than by combinations of small N and large T. The implications of these restrictions for ‘real-time’ data collection are noteworthy." @default.
- W2329799294 created "2016-06-24" @default.
- W2329799294 creator A5040292646 @default.
- W2329799294 creator A5090543333 @default.
- W2329799294 date "1987-09-01" @default.
- W2329799294 modified "2023-10-07" @default.
- W2329799294 title "Data Collection Strategies for Constant Wavelength Rietveld Analysis" @default.
- W2329799294 cites W1967392868 @default.
- W2329799294 cites W1972079413 @default.
- W2329799294 cites W1974792017 @default.
- W2329799294 cites W1993942653 @default.
- W2329799294 cites W1999998825 @default.
- W2329799294 cites W2000888633 @default.
- W2329799294 cites W2002415782 @default.
- W2329799294 cites W2004237145 @default.
- W2329799294 cites W2006265053 @default.
- W2329799294 cites W2008878870 @default.
- W2329799294 cites W2008980327 @default.
- W2329799294 cites W2009308817 @default.
- W2329799294 cites W2011071958 @default.
- W2329799294 cites W2013235808 @default.
- W2329799294 cites W2013485634 @default.
- W2329799294 cites W2016260972 @default.
- W2329799294 cites W2017411208 @default.
- W2329799294 cites W2017632458 @default.
- W2329799294 cites W2017675355 @default.
- W2329799294 cites W2021101359 @default.
- W2329799294 cites W2021183878 @default.
- W2329799294 cites W2021435045 @default.
- W2329799294 cites W2024703221 @default.
- W2329799294 cites W2024871205 @default.
- W2329799294 cites W2025691520 @default.
- W2329799294 cites W2033104476 @default.
- W2329799294 cites W2035547748 @default.
- W2329799294 cites W2038540944 @default.
- W2329799294 cites W2046951726 @default.
- W2329799294 cites W2047946709 @default.
- W2329799294 cites W2048678506 @default.
- W2329799294 cites W2054309788 @default.
- W2329799294 cites W2055616964 @default.
- W2329799294 cites W2056296607 @default.
- W2329799294 cites W2056970272 @default.
- W2329799294 cites W2060294733 @default.
- W2329799294 cites W2063486243 @default.
- W2329799294 cites W2063850782 @default.
- W2329799294 cites W2073545022 @default.
- W2329799294 cites W2075439969 @default.
- W2329799294 cites W2076894758 @default.
- W2329799294 cites W2085374874 @default.
- W2329799294 cites W2085575855 @default.
- W2329799294 cites W2089174174 @default.
- W2329799294 cites W2089981698 @default.
- W2329799294 cites W2094332733 @default.
- W2329799294 cites W2097509493 @default.
- W2329799294 cites W2127299066 @default.
- W2329799294 cites W2156220448 @default.
- W2329799294 cites W2166772130 @default.
- W2329799294 cites W2313706516 @default.
- W2329799294 cites W2321891346 @default.
- W2329799294 cites W4255913431 @default.
- W2329799294 doi "https://doi.org/10.1017/s088571560001263x" @default.
- W2329799294 hasPublicationYear "1987" @default.
- W2329799294 type Work @default.
- W2329799294 sameAs 2329799294 @default.
- W2329799294 citedByCount "44" @default.
- W2329799294 countsByYear W23297992942012 @default.
- W2329799294 countsByYear W23297992942015 @default.
- W2329799294 countsByYear W23297992942016 @default.
- W2329799294 countsByYear W23297992942019 @default.
- W2329799294 countsByYear W23297992942020 @default.
- W2329799294 countsByYear W23297992942021 @default.
- W2329799294 countsByYear W23297992942023 @default.
- W2329799294 crossrefType "journal-article" @default.
- W2329799294 hasAuthorship W2329799294A5040292646 @default.
- W2329799294 hasAuthorship W2329799294A5090543333 @default.
- W2329799294 hasConcept C10138342 @default.
- W2329799294 hasConcept C114614502 @default.
- W2329799294 hasConcept C115645028 @default.
- W2329799294 hasConcept C120665830 @default.
- W2329799294 hasConcept C121332964 @default.
- W2329799294 hasConcept C159985019 @default.
- W2329799294 hasConcept C162324750 @default.
- W2329799294 hasConcept C16345878 @default.
- W2329799294 hasConcept C168834538 @default.
- W2329799294 hasConcept C192562407 @default.
- W2329799294 hasConcept C198082294 @default.
- W2329799294 hasConcept C199360897 @default.
- W2329799294 hasConcept C204323151 @default.
- W2329799294 hasConcept C207114421 @default.
- W2329799294 hasConcept C2524010 @default.
- W2329799294 hasConcept C2777027219 @default.
- W2329799294 hasConcept C2778067643 @default.
- W2329799294 hasConcept C2780944729 @default.
- W2329799294 hasConcept C33923547 @default.
- W2329799294 hasConcept C34445779 @default.
- W2329799294 hasConcept C41008148 @default.
- W2329799294 hasConcept C520434653 @default.
- W2329799294 hasConcept C6260449 @default.