CheckCIF-PLAT931-949
PLAT931 Type_5 Test for Missed Twinning from FCF/CIF data
Check the proposed Twin Law. The entry in () represents the proposed rotation axis in reciprocal space and the one in [] the corresponding rotation is direct space. The relevant Twin Matrix can be found in the file '.ckf'.
Note: This test is based on F(calc) values calculated with the data in the CIF. This ALERT can be ignored when twinning has been addressed in the refinement (As indicated by the Absence of ALERT 930). Please check whether twinning is mentioned in the write-up of the paper.
(http://journals.iucr.org/services/cif/checking/PLAT931.html)
例：PLAT931_ALERT_5_G Found Twin Law ( 0 1 1)[ ] Estimated BASF
警告原因：可能有孪晶存在。
解决策略：加入栾晶法则按孪晶精修，如果不行需重新还原数据并拆分。
PLAT933 Type_2 Report number of OMIT records in embedded .res
This ALERT reports on the number of OMIT records (Reflections omitted from the least-squares refinement) in the CIF.
(http://journals.iucr.org/services/cif/checking/PLAT933.html)
例：PLAT933_ALERT_2_B Number of OMIT Records in Embedded .res File ... 4 Note
警告原因：使用了OMIT命令。
解决策略：无需解决，有合理解释即可。
PLAT934 Type_3 Report number of outliers
This ALERT reports on the number of reflections for which I(obs) and I(calc) differ more that 10 times SigmaW. (The latter being the square root of 1.0/weight for that reflection in the L.S. refinement). The reason for those deviations should be investigated. When shown to be systematic errors, those reflections are best removed from the refinement and their omission from the refinement reported in the experimental section of an associated paper.
(http://journals.iucr.org/services/cif/checking/PLAT934.html)
例：PLAT934_ALERT_3_B Number of (Iobs-Icalc)/SigmaW > 10 Outliers .... 2 Check
警告原因：有些高角度衍射点拟合误差较大(需上传fcf文件)。
解决策略：检查精修模型是否有问题，如果模型没有错可以OMIT掉这些点并在文章实验部分说明。
PLAT935 Type_2 Pseudo Extinction Parameter Test
Both significantly positive and significantly negative values should invoke a search for a likely cause and a corrective action.
(http://journals.iucr.org/services/cif/checking/PLAT935.html)
警告原因：存在伪消光参数。
解决策略：给出合理解释。
PLAT936 Type_2 Test for DAMP instruction in embedded .res
The reason for the use of a DAMP instruction in the final refinement job should be discussed/reported. 'DAMP 0.0' should not be used for small molecule refinement since it masks non-convergence.
(http://journals.iucr.org/services/cif/checking/PLAT936.html)
警告原因：精修中使用了DAMP命令。
解决策略：删除该命令，或者有合理解释即可。
PLAT937 Type_4 Report Exponential Term in SHELXL weight expression
The use of an exponential term in the SHELXL weight expression is not recommended in the final refinement stage (i.e. the third parameter in the SHELXL WGHT record).
(http://journals.iucr.org/services/cif/checking/PLAT937.html)
警告原因：在最终精修中使用了权重的指数项。
解决策略：删除WGHT中第三个参数后，重新精修生成CIF文件。
PLAT939 Type_3 Test for high not weight optimized S value
SHELXL optimizes two weight parameters to bring the S value close to 1.0. This ALERT reports the S value based on the supplied sigma(I) only. A large value of the last generally indicates the presence of large outliers in the data set. Examples are reflections 'measured' behind the beam stop. (See also ALERT_919). The latter are best left out with an OMIT instruction.
(http://journals.iucr.org/services/cif/checking/PLAT939.html)
例：PLAT939_ALERT_3_A Large Value of Not (SHELXL) Weight Optimized S . 738.33
警告原因：同PLAT083类似，权重值较大。
解决策略：OMIT掉误差较大的点，检查精修结构是否有问题，按照栾晶精修，或者升空间群。
PLAT940 Type_3 Test for wR2 refinement with all data
Apparently, observed data with I > n * sigma(I) were used in the F**2 least squares refinement, rather than all observed data.
(http://journals.iucr.org/services/cif/checking/PLAT940.html)
例：PLAT940_ALERT_3_A F**2 Refinement with I .GT. n * Sigma(I) only ..?
警告原因：可能是_reflns_threshold_expression项缺失。
解决策略：_reflns_number_total和_reflns_number_gt应相差较大，total指的是全部可观察衍射点，而 gt 通常是指>2\s(I)的衍射。即使是P-1空间群，这二个值的差也要在一倍以上。除非你的单晶是合金，且有极高对称性的。到原始数据中去寻找原因。
PLAT941 Type_3 Test fit Low Measured hkl Multiplicity
Multiple hkl measurements are advised, either of symmetry related reflections and/or at differen psi angle values around the diffrection vector normal to the diffracting PLAne. A good multiplicity is needed for a meaningful multi-scan based correction for absorption. Details can be found in the ckf file.
(http://journals.iucr.org/services/cif/checking/PLAT941.html)
例：PLAT941_ALERT_3_G Average HKL Measurement Multiplicity ........... 2.7 Low
警告原因：hkl多重性较低。
解决策略：可能需要重新收集数据。否则需要给出合理解释。
PLAT949 Type_5 Test for Poisson type Intensity Sigma Distribution
Check the validity of the observed reflection data.
(http://journals.iucr.org/services/cif/checking/PLAT949.html)
警告原因：可观测衍射数据无效。
解决策略：可能需要重新收集数据。否则需要给出合理解释。
