This is great! But before we all get carried away, a quick reality check
is in order. This isn't an area I've thought about, but my limited
understanding raises the following issues....
Given that an MTZ file contains a cell, an indexing of the data, and
possibly phases involving a choice of origin, the use of an MTZ file
immediately implies that some decision has been made about the spacegroup.
Selecting a different spacegroup from a list of possibilities may
involve reindexing, and/or changing origin/enantiomorph dependent
properties such as phases and HLs.
It would be possible for an MTZ file to say something like this:
'This file is generated assuming spacegroup X. Spacegroups X1, X2, X3,
X4, X5.... are also possible.'.
It should also be possible to compute on the fly whether a particular
column type needs to be modified for a different spacegroup.
How will we present this in user interfaces? As a starting point, until
a spacegroup has been settled upon, the user will need the option of
picking the spacegroup after having selected the MTZ. This means
potentially a reindexing step added to every single task - messy. As an
intermediate, being able to change the 'currently selected' spacegroup
as a separate task would be an improvement.
Phil Evans wrote:
I agree
On 9 Nov 2007, at 13:50, Eleanor Dodson wrote:
As I often say!!! The mtz format should carry point group and
alternate SGs - then be upgraded when youknow the correct SG..
Eleanor
Phil Evans wrote:
It just picks the first in the list, to store in the output MTZ file,
which can only handle one (92 < 96)
Phil
On 8 Nov 2007, at 22:26, Bryan W. Lepore wrote:
when pointless (1.2.0) finds enantiomorphic SG's, what is the
criterion for 'Selecting' one over the other?
e.g. i ran pointless on some tetragonal data, and the enantiomorphs
SG92/SG96 are selected as strong candidates
Spacegroup TotProb SysAbsProb Reindex Conditions
<P 41 21 2> ( 92) 0.956 0.956 00l:
l=4n, h00: h=2n (zones 1,2)
<P 43 21 2> ( 96) 0.956 0.956 00l:
l=4n, h00: h=2n (zones 1,2)
... then pointless reports :
Selecting space group P 41 21 2 as solutions are enantiomorphic
Best Solution space group P 41 21 2
... is that b/c pointless can only report one, and SG92 came up first?
-bryan
