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*To*:*idbrown@mcmaster.ca***Subject**:**Re: New version of CIF Core dictionary (2.4)****From**:**"Ralf W. Grosse-Kunstleve" <rwgk@yahoo.com>***Date*:*Sun, 17 Feb 2008 14:29:41 -0800 (PST)**Cc*:*comcifs@iucr.org**Reply-To*:*"Discussion list of the IUCr Committee for the Maintenance of the CIF Standard (COMCIFS)" <comcifs@iucr.org>*

Dear David, Sorry for the late review. I only have a few comments regarding details in the new DISTRIBUTED_DENSITY category. See below. Ralf ============================================================================== data_distributed_density_symmetry_multiplicity _enumeration_range 1:192 ============================================================================== The upper limit is rather arbitrary. It is true that the maximum multiplicity in the Int. Tab. is 192, but when working with group-subgroup relations (e.g. to analyze twinning) there could be unusual situations which require settings with larger multiplicities. I propose that the upper limit is removed. ============================================================================== data_distributed_density_symmetry_multiplicity _definition If the ring is at some arbitrary angle to the mirror plane, the mirror generates a second ring and both rings should be described independently. ============================================================================== This seems inconsistent with the general approach of only providing non-redundant atomic data (asymmetric unit). In my working experience, having to deal with explicit redundancy is usually cumbersome and prone to introduce ambiguities and errors. I'd very much prefer if the core dictionary mandated a non-redundant representation. ============================================================================== data_distributed_density_Uiso _definition ; The factor exp(-Ux^-2^) is applied to all parts of the ============================================================================== ^^^^ 2 pi ^2^ ? The formula for the Debye-Waller factor (atomic Uiso) is exp(-2 pi^2^ U d^-2^) I find it misleading that the 2 pi^2^ is folded into _distributed_density_Uiso. For consistency, I'd change the definition to: exp(-2 pi^2^ Ux^-2^) Another commonly used notation for the isotropic displacement parameter is "beta" (greek letter), with this definition: exp(-beta d^-2^) This suggests the name _distributed_density_beta_iso. However, I'd prefer to keep _distributed_density_Uiso, but with a definition compatible with the atomic Uiso. ============================================================================== 6. _exptl_absorption_correction_T_max, *_T_min ^^^^ wrong name exptl_transmission_factor_max and *_min ============================================================================== ^ missing underscore _______________________________________________ comcifs mailing list comcifs@iucr.org http://scripts.iucr.org/mailman/listinfo/comcifs

**Follow-Ups**:**Re: New version of CIF Core dictionary (2.4)**(David Brown)

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