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Parametric Rietveld refinement.

Stinton GW, Evans JS - J Appl Crystallogr (2007)

Bottom Line: In this paper the method of parametric Rietveld refinement is described, in which an ensemble of diffraction data collected as a function of time, temperature, pressure or any other variable are fitted to a single evolving structural model.Parametric refinement offers a number of potential benefits over independent or sequential analysis.It can lead to higher precision of refined parameters, offers the possibility of applying physically realistic models during data analysis, allows the refinement of 'non-crystallographic' quantities such as temperature or rate constants directly from diffraction data, and can help avoid false minima.

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Affiliation: Department of Chemistry, University of Durham, UK.

ABSTRACT
In this paper the method of parametric Rietveld refinement is described, in which an ensemble of diffraction data collected as a function of time, temperature, pressure or any other variable are fitted to a single evolving structural model. Parametric refinement offers a number of potential benefits over independent or sequential analysis. It can lead to higher precision of refined parameters, offers the possibility of applying physically realistic models during data analysis, allows the refinement of 'non-crystallographic' quantities such as temperature or rate constants directly from diffraction data, and can help avoid false minima.

No MeSH data available.


Cell parameter of ZrP2O7 derived from independent refinements (open symbols) and parametric fitting using a polynomial temperature correction (closed symbols). Data are plotted against the furnace set temperature and Rietveld-refined temperature, respectively.
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fig6: Cell parameter of ZrP2O7 derived from independent refinements (open symbols) and parametric fitting using a polynomial temperature correction (closed symbols). Data are plotted against the furnace set temperature and Rietveld-refined temperature, respectively.

Mentions: The key quantity from these independent refinements, the pseudo-cubic cell of ZrP2O7, is shown in Fig. 6 ▶. Whilst the phase transition from the 3 × 3 × 3 orthorhombic to the 1 × 1 × 1 cubic structure is clearly visible, the phase transition temperature (512–527 K) is significantly lower than found by calorimetry (567 K). However, significant discrepancies are also observed between the expected and observed temperature dependence of cell parameters of the internal standards.


Parametric Rietveld refinement.

Stinton GW, Evans JS - J Appl Crystallogr (2007)

Cell parameter of ZrP2O7 derived from independent refinements (open symbols) and parametric fitting using a polynomial temperature correction (closed symbols). Data are plotted against the furnace set temperature and Rietveld-refined temperature, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2483475&req=5

fig6: Cell parameter of ZrP2O7 derived from independent refinements (open symbols) and parametric fitting using a polynomial temperature correction (closed symbols). Data are plotted against the furnace set temperature and Rietveld-refined temperature, respectively.
Mentions: The key quantity from these independent refinements, the pseudo-cubic cell of ZrP2O7, is shown in Fig. 6 ▶. Whilst the phase transition from the 3 × 3 × 3 orthorhombic to the 1 × 1 × 1 cubic structure is clearly visible, the phase transition temperature (512–527 K) is significantly lower than found by calorimetry (567 K). However, significant discrepancies are also observed between the expected and observed temperature dependence of cell parameters of the internal standards.

Bottom Line: In this paper the method of parametric Rietveld refinement is described, in which an ensemble of diffraction data collected as a function of time, temperature, pressure or any other variable are fitted to a single evolving structural model.Parametric refinement offers a number of potential benefits over independent or sequential analysis.It can lead to higher precision of refined parameters, offers the possibility of applying physically realistic models during data analysis, allows the refinement of 'non-crystallographic' quantities such as temperature or rate constants directly from diffraction data, and can help avoid false minima.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, University of Durham, UK.

ABSTRACT
In this paper the method of parametric Rietveld refinement is described, in which an ensemble of diffraction data collected as a function of time, temperature, pressure or any other variable are fitted to a single evolving structural model. Parametric refinement offers a number of potential benefits over independent or sequential analysis. It can lead to higher precision of refined parameters, offers the possibility of applying physically realistic models during data analysis, allows the refinement of 'non-crystallographic' quantities such as temperature or rate constants directly from diffraction data, and can help avoid false minima.

No MeSH data available.