CheckCIF-PLAT970-978

PLAT970 Type_5 Test/Report Electron Diffraction

A structure based on electron diffraction is reported. Please check for the use of proper electron scattering factors in the refinement. X-ray scattering factors are not appropriate for a SHELXL based refinement.

(http://journals.iucr.org/services/cif/checking/PLAT970.html)

警告原因：电子衍射数据。

解决策略：换用合适的精修程序进行精修。

PLAT971 Type_2 Test for large positive calculated residual density

Larger than expected residual density maximum outside metal atom locations. This might be caused by unaccounted for twinning, wrongly assigned atom types, unaccounted for solvent and other model errors.

(http://journals.iucr.org/services/cif/checking/PLAT971.html)

例：PLAT971_ALERT_2_C Check Calcd Residual Density 1.23A From O5 1.73 eA-3

警告原因：原子存在大量较重Q峰。

解决策略：Q峰游离检查是否有原子未指认，Q峰如果在轻原子周围检查是否可以无序处理，在重原子周围需要重新吸收校正或者收集数据。使用Shel 999 0.84切去部分高角度点可缓解此警告。最后检查是否数据足够好，是否存在栾晶。

PLAT972 Type_2 Test for large negative calculated residual density

Larger than expected residual density minimum outside metal atom locations. This might be caused by unaccounted for twinning, wrongly assigned atom types and other model errors.

(http://journals.iucr.org/services/cif/checking/PLAT972.html)

例：PLAT972_ALERT_2_A Check Calcd Residual Density 2.39A From C1 -4.35 eA-3

警告原因：原子存在大量较重Q峰。

解决策略：Q峰游离检查是否有原子未指认，Q峰如果在轻原子周围检查是否可以无序处理，在重原子周围需要重新吸收校正或者收集数据。使用Shel 999 0.84切去部分高角度点可缓解此警告。最后检查是否数据足够好，是否存在栾晶。

PLAT973 Type_2 Test for large positive density on metal atom

Larger than expected residual density maximum on metal atom location. This might be caused by unaccounted for twinning, wrongly assigned atom types and other model errors. Another cause may be a SHELXL 'DAMP 0 0' instruction for a non-converged refinement.

(http://journals.iucr.org/services/cif/checking/PLAT973.html)

例：PLAT973_ALERT_2_C Check Calcd Positive Residual Density on Co1 1.40 eA-3

警告原因：原子存在大量较重Q峰。

解决策略：Q峰游离检查是否有原子未指认，Q峰如果在轻原子周围检查是否可以无序处理，在重原子周围需要重新吸收校正或者收集数据。使用Shel 999 0.84切去部分高角度点可缓解此警告。最后检查是否数据足够好，是否存在栾晶。

PLAT974 Type_2 Test for large negative density close to metal atom

Larger than expected residual density minimum on metal atom location. This might be caused by unaccounted for twinning, wrongly assigned atom types and other model errors. Another cause may be a SHELXL 'DAMP 0 0' instruction for a non-converged refinement.

(http://journals.iucr.org/services/cif/checking/PLAT974.html)

例：PLAT974_ALERT_2_A Large Calcd. Negative Residual Density on Zn1 -3.02 eA-3

警告原因：原子存在大量较重Q峰。

解决策略：Q峰游离检查是否有原子未指认，Q峰如果在轻原子周围检查是否可以无序处理，在重原子周围需要重新吸收校正或者收集数据。使用Shel 999 0.84切去部分高角度点可缓解此警告。最后检查是否数据足够好，是否存在栾晶。

PLAT975 Type_2 Test for positive density near N or O

Positive density found in a difference density map at a position within bonding distance for a hydrogen atom from a nitrogen or oxygen atom. A possible reason can be a missing hydrogen atom. Also check for tautomerism.

(http://journals.iucr.org/services/cif/checking/PLAT975.html)

例：PLAT975_ALERT_2_C Check Calcd Residual Density 0.97A From O6 0.60 eA-3

警告原因：原子存在大量较重Q峰。

解决策略：Q峰游离检查是否有原子未指认，Q峰如果在轻原子周围检查是否可以无序处理，在重原子周围需要重新吸收校正或者收集数据。使用Shel 999 0.84切去部分高角度点可缓解此警告。最后检查是否数据足够好，是否存在栾晶。

PLAT976 Type_2 Test for negative density near N or O

Negative density found in a difference density map at a location within bonding distance for a hydrogen atom from a nitrogen or oxygen atom. A possible reason can be a misassigned hydrogen atom. Also check for tautomerism.

(http://journals.iucr.org/services/cif/checking/PLAT976.html)

例：PLAT976_ALERT_2_C Check Calcd Residual Density 0.83A From O6 -0.76 eA-3

警告原因：原子存在大量较重Q峰。

解决策略：Q峰游离检查是否有原子未指认，Q峰如果在轻原子周围检查是否可以无序处理，在重原子周围需要重新吸收校正或者收集数据。使用Shel 999 0.84切去部分高角度点可缓解此警告。最后检查是否数据足够好，是否存在栾晶。

PLAT977 Type_2 Test for negative density on H-atom positions

Negative density found in a difference density map at a H-atom location. A reason might be an incorrect AFIX instruction.

(http://journals.iucr.org/services/cif/checking/PLAT977.html)

例：PLAT977_ALERT_2_C Check the Negative Difference Density on H1A -0.34 eA-3

警告原因：原子存在大量较重Q峰。

解决策略：Q峰游离检查是否有原子未指认，Q峰如果在轻原子周围检查是否可以无序处理，在重原子周围需要重新吸收校正或者收集数据。使用Shel 999 0.84切去部分高角度点可缓解此警告。最后检查是否数据足够好，是否存在栾晶。

PLAT978 Type_2 Report number of cases with positive density on C-C bonds

Difference density maps generally show residual densities on C-C bonds. A significant number may indicate good data. Cases where this number is zero should be investigated for a reason.

(http://journals.iucr.org/services/cif/checking/PLAT978.html)

例：PLAT978_ALERT_2_G Number C-C Bonds with Positive Residual Density. 1 Info

警告原因：C-C键上有残余电子密度。

解决策略：无需解决，有合理解释即可。