CheckCIF-PLAT911-920

PLAT911 Type_3 Test for missing reflections between Theta(Min)and sinth/lambda=0.6

Possible causes: Missing cusp of data (due to rotation about one axis), deleted (overflow) reflections or improper strategy (orthorhombic for monoclinic crystal etc.)

(http://journals.iucr.org/services/cif/checking/PLAT911.html)

例：PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L = 0.600

警告原因：缺少部分衍射点。

解决策略：可不解决，有合理解释即可。也可重新收集数据补齐缺失数据。

PLAT912 Type_4 Test for missing reflections above Sin(TH)/Lambda = 0.6

Possible causes: Missing cusp of data (due to rotation about one axis), deleted (overflow) reflections or improper strategy (orthorhombic for monoclinic crystal etc.)

(http://journals.iucr.org/services/cif/checking/PLAT912.html)

例：PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L= 0.600 4 Note

警告原因：缺少部分衍射点。

解决策略：可不解决，有合理解释即可。也可重新收集数据补齐缺失数据。

PLAT913 Type_3 Test for missing strong reflections

This ALERT reports the number of missing reflections with Fc**2 values greater than the largest Fc**2 value in the FCF. Possible causes: Missing cusp of data (due to rotation about one axis), deleted (overflow) reflections or improper strategy (orthorhombic for monoclinic crystal etc.) or behind the beamstop.

(http://journals.iucr.org/services/cif/checking/PLAT913.html)

例：PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF .... 2 Note

警告原因：缺少部分衍射点。

解决策略：可不解决，有合理解释即可。也可重新收集数据补齐缺失数据。

PLAT914 Type_3 Test for absence of Bijvoet Pairs in non-centro structure

This ALERT reflects the notion that a dataset should contain a sufficient number of Bijvoet (Friedel) pairs for the reliable determination of the absolute structure of a non-centrosymmetric crystal structure. This test is invoked when a Flack parameter value is specified.

Note: SHELXL97 will calculate/report a Flack parameter value even for refinement against Friedel merged data. Remove the Flack entry from the CIF.

(http://journals.iucr.org/services/cif/checking/PLAT914.html)

例：PLAT914_ALERT_3_C No Bijvoet Pairs in FCF for Non-centro Structure Please Check

警告原因：非心空间群结构缺少Bijvoet对。

解决策略：一般不会出现，有合理解释即可。

PLAT915 Type_3 Test for low Friedel Pair Coverage in non-centro structure

This ALERT reflects the notion that a dataset should contain a sufficient number of Bijvoet (Friedel) pairs for the reliable determination of the absolute structure of a non-centrosymmetric crystal structure. A Friedel coverage that deviates significantly from 100 percent may bias/invalidate the value of the Flack parameter.

(http://journals.iucr.org/services/cif/checking/PLAT915.html)

例：PLAT915_ALERT_3_B Low Friedel Pair Coverage…42%

解决策略：数据收集不当，与精修没关系，估计是无心当有心的收了；不传fcf就没事了，如果不定绝对构型有这个错误无所谓。

PLAT916 Type_2 Test for differing Flack x and Hooft y Parameter values

The Hooft y Parameter is calculated independently from the Bijvoet differences and should have a value similar (observing the s.u.'s) to that of the Flack x Parameter.

See: Hooft, R.W.W, Straver, L.H. & Spek, A. L. (2008). J. Appl, Cryst. 41, 96-103. Thompson, A. L. & Watkin, D.J. (2009). Tetrahedron: Asymmetry, doi:10.1016/j.tetasy.2009.02.025

Large differences may arise in cases where the Flack parameter was not done with BASF/TWIN or with essentially centrosymmetric data.

See: Flack, H. D., Bernardinelli, G, Clemente, D. A., Linden, A. Spek, A. L. (2006) Acta Cryst. B62, 695-701.

(http://journals.iucr.org/services/cif/checking/PLAT916.html)

例：PLAT916_ALERT_2_G Hooft y and Flack x Parameter values differ by . 0.20

警告原因：Hooft系数y和Flack系数x之间有差异。

解决策略：有合理解释即可。

PLAT917 Type_2 Test/Report whether FCF is based on a BASF/TWIN refinement

The contribution of F(-h,-k,-l) to F(h,k,l) is likely not included in the FCF file. This usually indicates that the Flack parameter was NOT determined with a BASF/TWIN type of refinement.

(http://journals.iucr.org/services/cif/checking/PLAT917.html)

警告原因：结构进行了孪晶精修。

解决策略：一般无需处理，有合理解释即可。

PLAT918 Type_3 Test for reflections with I(obs) << I(calc)

This ALERT reports on the number of reflections with (Fo**2 - Fc**2) / Sigma(Fo**2) < - 100.0. In case of strong reflections this might be due to extinction (to be addressed with the refinement of an extinction parameter. Otherwise Those reflections are better removed from the final refinement since they are in systematic error. Of course, a valid reason for this problem should be found.

(http://journals.iucr.org/services/cif/checking/PLAT918.html)

例：PLAT918_ALERT_3_C Reflection(s) with I(obs) much smaller I(calc)

警告原因：观测到强度远小于计算得到强度。

解决策略：OMIT这些点即可。

PLAT919 Type_3 Test for reflections effected by the beamstop

This ALERT reports the number of reflections with intensities seriously effected by the beamstop. Reflections are counted for which theta < 3 Degrees and (Fo**2 - Fc**2) / sqrt(weight) < - 10.0. Those reflections are better removed from the final refinement since they are in systematic error.

(http://journals.iucr.org/services/cif/checking/PLAT919.html)

例：PLAT919_ALERT_3_B Reflection # Likely Affected by the Beamstop ... 2 Check

警告原因：有些低角度衍射点拟合误差较大，可能是由于仪器的原因(需上传fcf文件)。

解决策略：在lst文件中找出误差大的点，OMIT掉即可。

去LST文件里：

Most Disagreeable Reflections (* if suppressed or used for Rfree)

下面找到前两组的HKL

去ins文件里填写如下命令后精修即可

OMIT H1 K1 L1

OMIT H2 K2 L2

若使用OLEX2，则可以直接在“Bad Reflections”菜单栏(下图所示)中将误差大的衍射点OMIT。

PLAT920 Type_1 Test for TH(Max) Consistency between CIF & FCF

Check reflection statistics of the data in the FCF for consistency with the data reported in the CIF. A difference usually indicates an edited CIF or an FCF file that was not created in the same SHELXL run where the CIF was created.

(http://journals.iucr.org/services/cif/checking/PLAT920.html)

例：PLAT920_ALERT_1_A Theta(Max) in CIF and FCF Differ by ........... 2.92 Deg.

警告原因：CIF和FCF中最大θ角有差异。

解决策略：一般不会出现，重新精修生成CIF文件。