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[交流] 关于XRD粉末衍射PDF卡片Quality Mark问题已有7人参与

当你看到一个PDF卡片数据，不要轻易迷信它，你先看看它数据是否可靠，级别高不高，如图中我用红色圈起来的地方。PDF卡片按数据来源和可靠性分了好几个级别，每个级别都用一个字符来表示，下面是ICDD对这些级别的介绍：

Quality Mark
The quality mark option allows the user to select only patterns for which the appropriate quality mark is prescribed. The quality mark selection can be "*" (star quality pattern); an "I" (indexed pattern); a "0" (low precision pattern); a "C" (calculated pattern); an "R" (Rietveld pattern); or a "blank" (undefined quality pattern). The user may also select "All" (which is also the default value); that causes the program to select all patterns independently of the quality mark.

Any one of the following Quality Marks can be chosen:

"*" A "Star" quality pattern represents high quality diffractometer or Guinier data; the chemical composition is well characterized; intensities have been measured objectively; and no serious systematic errors exist. The average delta 2theta is less than 0.03 deg.

"I" An "Indexed" quality mark indicates that the pattern has been indexed (thus is almost certainly single phase). There is a reasonable range and even spread in intensities; there are no serious systematic errors and the average delta 2theta is less than 0.06 deg.

"0" A "Zero" quality mark means that the diffraction data have been taken on poorly characterized material or that the data are known (or suspected) to be of low precision.

"B" A "Blank" quality mark is assigned to patterns which do not meet the "*", "I", or "0" criteria

"R" A "Rietveld" quality mark is used for patterns where it is clear that the d-values are directly the result of Rietveld refinement of the data. However, Rietveld refinements are accepted only in unusual cases.

"C" A "Calculated" quality mark is assigned to those patterns which have been calculated from single crystal data. C patterns generally have very precise d-values, but the intensities may not reflect what is obtained in an experimental pattern.

Selection of one of these quality mark restrictions will limit the patterns retrieved to patterns containing that mark. For example, selection of "C" patterns will retrieve only calculated patterns.

希望这个介绍能对大家以后分析数据有所帮助。

[ Last edited by gyliu on 2012-5-31 at 16:12 ]

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