I've wondered a couple of things on this score:
--What is the general range in uncertainties of cell parameters? I assume there's a huge range as a function of resolution esp., but it would be nice to have a general feeling for it.
--Has anyone experimented with implementing a cell parameter step in refinement? I would think the effect would be small but still perhaps significant, especially at lower resolution and/or when cell parameters are not known very precisely.
*******************************************
Jacob Pearson Keller, PhD
Research Scientist
HHMI Janelia Research Campus
email: [log in to unmask]
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________________________________________
From: CCP4 bulletin board [[log in to unmask]] on behalf of Tim Gruene [[log in to unmask]]
Sent: Tuesday, July 26, 2016 11:15 AM
To: [log in to unmask]
Subject: Re: [ccp4bb] Why don't we quote errors on unit cell constants in MX
Dear Graeme,
XDS reports standard uncertainties of the unit cell parameters in CORRECT.LP
and I recently started to include this information in publications. So at
least one of us does ;-)
I also include this information in the SHELXL ZERR keyword - as fas as I
understand it affects the s.u. for coordinates and other things you can
calculate with SHELXL.
The information is not too obvious to access, and it only have limited
information content. Maybe that's why it isn't quoted.
Best,
Tim
On Tuesday, July 26, 2016 03:07:03 PM Graeme Winter wrote:
> Dear CCP4BB
>
> Does anyone know why we don't quote standard uncertainties on unit cell
> constants in the way that the small molecule community do? It would seem in
> the new world of multi-crystal data sets and serial crystallography some
> idea of the measure of ignorance would be particularly valuable.
>
> I'm not worried about whether they are "right" or "true" just interested in
> why we don't quote them...
>
> An example for thaumatin may look like this, for example:
>
> Unit cell (with estimated std devs):
> 57.7841(1) 57.7841(1) 149.9963(3)
> 90.0000(0) 90.0000(0) 90.0000(0)
>
> (in other news, there is no place to store this information in an MTZ
> file...)
>
> Thanks & best wishes Graeme
>
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