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Re: Transfer from msCIF: refine_ls_class category

  • To: Multiple recipients of list <coredmg@iucr.org>
  • Subject: Re: Transfer from msCIF: refine_ls_class category
  • From: Gotzon Madariaga <wmpmameg@lg.ehu.es>
  • Date: Wed, 14 Oct 1998 17:52:17 +0100 (BST)
Dear colleagues

I have been really busy along the last three weeks during the installation
and testing of a new diffractometer. I have read again the e-mails
concerning the _refine_ls_class and related categories. I think that Brian
explained quite well the relationships among the different categories and
I agree with the introduction of _diffrn_refln_class_code. Also I would
remove _diffrn_reflns_number_of_classes (I have already done this in the
MS dictionary). It is just a surviving item from the first draft of the
dictionary where I put several (redundant) items for checking the
consistency of a CIF and thinking in an extensive use of _type_construct.
By the way I think we should experiment with this item for restricting
values in terms of other values present in a CIF or block, (what about,
for example, with _chemical_optical_rotation?). 

Nevertheless I do not agree with the separation in experimental and
refinement classes. Perhaps you know several counterexamples, but in my
opinion any classification of intensities at the refinement stage should
be linked to the measurement stage. For example one could ask always how
many reflections have been measured for a certain parity group or how many
first order satellites. That is why I introduced _diffrn_reflns_class_code
as the parent for the rest of codes. The same would be applicable to the
shells. 

Concerning _diffrn_reflns_class_d_res_low and
_diffrn_reflns_class_d_res_high, the idea is to give the degree of
completeness for each class. They should be considered as an extension of
_diffrn_reflns_theta_max and _diffrn_reflns_theta_min, but removing the
wavelength dependence of the latter items. 


Gotzon


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Gotzon Madariaga                          |   E-mail: wmpmameg@lg.ehu.es
Dpto. Fisica de la Materia Condensada     |
Facultad de Ciencias                      |   Phone: 34 4 4647700 (Ext. 2489)
Universidad del Pais Vasco                |   FAX  : 34 4 4648500
Apdo. 644                                 |
48080 Bilbao (SPAIN)                      |
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