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Dear Nicholas,
not sure whether it will work - learning by doing:
You might integrate the P213 data set in the subgroup P212121 with the
real P212121 data as reference data set. At least XDS will then choose
consistent indexing.
As last step you repeat the CORRECT step with the space group assigned
to P213 (CORRECT might actually pick the right lattice symmetry
automatically) this should not change the indexing IF XDS considers it
possible.
Best,
Tim
On 01/17/2013 03:08 PM, Nicholas Keep wrote:
> I have a structure which normally crystallises in P213 but one data
> set the edges became slightly non-equivalent in length by a couple
> of angstroms and the data process in P212121
>
> P212121 symmetry operators appears to be a subset of P213
>
> http://img.chem.ucl.ac.uk/sgp/large/019az1.htm
> http://img.chem.ucl.ac.uk/sgp/large/198az1.htm
>
> (Not absolutely sure the above are world viewable)
>
> Naively I expected the two structures to roughly align. However
> they don't there appears to be some change of axes between them.
> The transform of the P213 onto the P212121 structure is 0.03345
> -0.9977 -0.0598 -0.9994 0.03402 -0.08653 0.01066 0.05929 -0.9982
> -18.16 -57.18 21.39
>
> This is clearly close to
>
> 0 -1 0 -1 0 0 0 0 -1 -0.25 -.75 0.25 in fractionals.
>
> Applying either the exact transformation or the regularised one
> with ether indexing of p213 ie original and k h -l
> http://www.ccp4.ac.uk/html/reindexing.html the rfactors are well
> above 50% and don't drop.
>
> Any suggestions of what I am doing wrong or is this not going to
> work (tried MR into the reindexed data and that does not align
> either- in fact I have tried quite a lot things)
>
> The reason for trying to get the two structures on the same axes is
> to compare the electron densities. The P212121 seems to have some
> of the disorder loops better defined.
>
> Using the Coot transform map by LSQ superpose is quite good BUT it
> would be better if it were another map other than the refinement
> map that is transformed as I then want to refine the unmoved
> structure into the unmoved map guided by the moved map and that
> involved a lot of changes of map selection.
>
> Thanks nick
>
>
>
- --
- --
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
GPG Key ID = A46BEE1A
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