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Laboratory of X-ray Diffractometry and Spectrometry

QUALITY MARKS (QM) PDF cards have quality marks to indicate how reliable the data is.

 Star (S, +). Indicates the pattern represents high-quality diffractometer data. The chemical composition has been well characterized. The intensities have been measured objectively and no serious systematic errors exist. No un-indexed, space group extinct or impurity reflections are present. The average Δ2Θ (difference between measured 2 Θ and calculated 2Θ from unit cell) is less than 0,03 deg for qualifying (measured) reflections.

(Good range and an even spread of intensity. Completeness of a pattern is sensible when factors such as pseudosymmetry are taken into account. Each reflection with d-value less than or equal to 2.500A has at least 3 significant figures after the decimal point. Reflections with d-value less than or equal to 1.2000A have at least 4 significant figures after the decimal point).

 Indexed (I). Indicates the pattern has been indexed (thus is almost certainly single phase) and no serious systematic errors exist. The maximum number of un-indexed, space group extinct or impurity reflections is two, but none of these reflections is among the strongest eight lines. The average Δ2Θ is less than 0,06 deg for qualifying reflections.

(There is a reasonable range and even spread in intensities. Completeness of the pattern is sen-sible. Reflections with d-value less than or equal to 2.000A have at least three significant figures after the decimal point. No qualifying reflection has an absolute Δ2Θ greater than or equal to 0.20 degrees).

 Blank (B). Indicates the pattern does not meet the Star, Indexed, or Low-Precision criteria.

 Doubtful (O, ?). Indicates the diffraction data have been taken on poorly characterized material and commonly no unit cell is reported. It is  known or suspected problems such as preferred orientation or the data to be of low precision. The number of un-indexed, space group extinct or impurity reflections is three or more. One of the three strongest reflections is un-indexed.

(Data from a multi-phase mixture. Data from a phase poorly-characterized chemically. The "O" quality mark is commonly assigned to patterns for which no unit cell is reported unless qualifying information indicates a single-phase material. Usually, the editor has inserted a comment to explain why the "O" was assigned. For patterns with a unit cell, the following parameters are used to suggest the presence of two of more phases).

 Calculated (C). Indicates the powder pattern was calculated from single-crystal structural parameters, for which the structural refinement R-factor was < 0.10. C patterns generally have very precise d-values, but the intensities may not reflect what is obtained in an experimental pattern. 

 Rietveld (R). Indicates the d-values are directly the result of Rietveld refinement of the data.

 Hypothetical (H). Indicates the structure is calculated theoretically from the atomic positions and thermal parameters of an isostructural compound.

Updated: 23.7.2018 10:39, Author: Jan Prchal

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