CheckCIF-CRYSS02

PROC-NAME: CRYSS02 Type_3

PURPOSE: To check that the values of _exptl_crystal_size_* are not larger than expected.

PROCEDURE:

(1) IF _exptl_crystal_size_min > 0.6 && _diffrn_radiation_type != neutron

issue ALERT B

         "Alert B The value of _exptl_crystal_size_min is > 0.6"

(2) IF _exptl_crystal_size_mid > 0.8 && _diffrn_radiation_type != neutron

issue ALERT B

         "Alert B The value of _exptl_crystal_size_mid is > 0.8"

(3) IF _exptl_crystal_size_max > 1.0 && _diffrn_radiation_type != neutron

issue ALERT B

         "Alert B The value of _exptl_crystal_size_max is > 1.0"

      The crystal must be smaller than size of the incident beam at the crystal. For most diffractometers with fine-focus X-ray tubes and monochromated radiation, this size is unlikely to be much greater than 0.5 mm. Note that increasing the collimator diameter will not necessarily increase the size of the incident beam at the crystal. If the crystal used in the data collection is larger than the incident beam, then unpredictable errors in intensities will occur due to the varying amounts of the crystal in the beam for different reflection positions. If you obtain an alert about crystal size, then data should be collected with a smaller crystal. For the above reasons, it is recommended that crystals be generally smaller than 0.5 mm along any edge.

      If you used neutrons and obtained an alert about the crystal size, then you have forgotten to set _diffrn_radiation_type 'neutron'.

(http://journals.iucr.org/services/cif/checking/CRYSS_02.html)

目的：检查_exptl_crystal_size_*的值是否超出预期。

过程：

(1)若_exptl_crystal_size_min > 0.6且_diffrn_radiation_type不为neutron

则发布B级警告

         "Alert B The value of _exptl_crystal_size_min is > 0.6"

(2)若_exptl_crystal_size_mid > 0.8且_diffrn_radiation_type 不为 neutron

则发布B级警告

         "Alert B The value of _exptl_crystal_size_mid is > 0.8"

(3)若_exptl_crystal_size_max > 1.0且_diffrn_radiation_type不为neutron

则发布B级警告

         "Alert B The value of _exptl_crystal_size_max is > 1.0"

        晶体必须小于晶体上入射光束的大小。对于大多数具有精细聚焦X射线管和单色辐射的衍射仪，该尺寸不太可能远大于0.5 mm。注意，增加准直器直径不一定会增加晶体处入射光束的尺寸。若数据收集中使用的晶体大于入射光束，则由于光束中不同衍射位置的晶体数量的变化，强度上会发生不可预测的误差。若出现关于晶体尺寸的警告，则应当使用较小的晶体收集数据。由于上述原因，建议晶体的任何边缘通常小于0.5 mm。

        若你使用中子衍射收集数据的数据出现晶体尺寸警告，那么想必你是忘了将_diffrn_radiation_type设为“neutron”。

警告原因：晶体尺寸超出限制大小。

解决策略：将晶体尺寸改为合适的数值。