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Re: What does it mean for _diffrn_ambient_temperature and_cell_measurement_temperature to be different?

Thank you all for your insights and information.
I think the best way forward is simply to clarify in the definitionsthat the cell_measurement_temp/pressure items would only differ(slightly) from _diffrn_ambient_temp/pressure where the cell wasdetermined separately from the diffraction pattern. If these items areabsent their default values can be taken from the corresponding_diffrn_ambient items. Making the reverse deduction can be a matter ofpolicy for CIF curators.
If there are no objections, I will make the updates to the coredictionary. You can follow along and comment here:https://github.com/COMCIFS/cif_core/issues/294
On Tue, 18 Jan 2022 at 20:19, Spek, A.L. (Ton) <A.L.Spek@uu.nl> wrote:>> James,> A good point.> IUCr/PLATON/checkCIF sends out an A-level ALERT for this. Referees should have picked this up.> Older SHELXL versions put in a default value for those values in the CIF they generated (Room Temperature)> A quick check of the CIF's for all structures published in the 2021 issues of Acta Cryst. E77 shows that there are no inconsistencies there.>> Best wishes>> Ton>>> Op 18-01-2022 06:47 heeft coreDMG namens James H via coreDMG <coredmg-bounces@iucr.org namens coredmg@iucr.org> geschreven:>>     Happy New Year everybody.>>     Here is our first issue for the year:>>     At first glance it would appear to me that _diffrn_ambient_temperature and>     _cell_measurement_temperature are describing the same thing. There may>     have been a difference in the past when using point detectors and the>     cell was determined separately to the data collection, but for>     anything collected on an area detector I would have expected these>     values to be the same. However, I've noticed from looking at around>     10000 files from the COD that, of the files that have both data names,>     around 1% have different numbers. I'm wondering what this could>     possibly mean, especially when the two numbers are very different e.g.>     150K and 296K. Given that the cell parameters are necessary to obtain>     absolute distances from fractional coordinates, if the diffraction>     data are collected at a different temperature to the cell measurement,>     then surely these atomic distances would be incorrect?  How do the>     database curators handle this? How are software authors interpreting>     these two data names for output or input?>>     If you agree that there is no way these numbers should be>     significantly different, suggestions on how to fix the situation are>     welcome. Personally I would deprecate _cell_measurement_temperature or>     state that it is only used when the cell is measured separately to the>     main diffraction data set.>>     James.>>     -->     T +61 (02) 9717 9907>     F +61 (02) 9717 3145>     M +61 (04) 0249 4148>     _______________________________________________>     coreDMG mailing list>     coreDMG@iucr.org>     http://mailman.iucr.org/cgi-bin/mailman/listinfo/coredmg>

-- T +61 (02) 9717 9907F +61 (02) 9717 3145M +61 (04) 0249 4148_______________________________________________coreDMG mailing listcoreDMG@iucr.orghttp://mailman.iucr.org/cgi-bin/mailman/listinfo/coredmg

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