Dear Eric,

For sg  R3, you have two main settings:
R3:H : a=b!=c, 90,90, 120
R3:R: a=b=c, alpha=beta=gamma!=90
They are related of course.

please check :

http://cci.lbl.gov/cctbx/browse_settings.html

and type

R3 in the space group box.

This will give two space group info charts that you can have a look at.

In this case (159.0, 159.0, 159.0, 109.0, 109.0, 109.0; R3:R) you actually will get
R 3:H  258.89 258.89 162.66 90.00 90.00 120.00
after transforming to the reference setting.

Note that higher metric symmetry is possible as well in this case, suggesting cubic symmetry:

----------------------
Input crystal symmetry
----------------------
Unit cell:  (159.0, 159.0, 159.0, 109.0, 109.0, 109.0)
Unit cell volume:  3147178.10148
Space group:  R 3 :R

( ...... )

----------------------
Compatible spacegroups
----------------------

Spacegroups compatible with a specified point group
**and** with the systematic absenses specified by the
input space group, are listed below.

Spacegroup candidates in point group R 3 2 :R:
  * R 3 2 :H  258.89 258.89 162.66 90.00 90.00 120.00

Spacegroup candidates in point group Hall:  I 2 2 3 (y+z,x+z,x+y):
  * I 2 3  184.66 184.66 184.66 90.00 90.00 90.00
  * I 21 3  184.66 184.66 184.66 90.00 90.00 90.00

Spacegroup candidates in point group R 3 :R:
  * R 3 :H  258.89 258.89 162.66 90.00 90.00 120.00

Spacegroup candidates in point group Hall:  I 4 2 3 (y+z,x+z,x+y):
  * I 4 3 2  184.66 184.66 184.66 90.00 90.00 90.00
  * I 41 3 2  184.66 184.66 184.66 90.00 90.00 90.00


(This list was generated with the following command:

iotbx.ehms --unit_cell='159 159 159 109 109 109' --space_group=R3:R.

In the absense of perfect twinning, xtriage should be able to figure out what the proper space group is)

Making something in the cctbx, something like this (not tested) should work I think:

from cctbx import uctbx
from cctbx import crystal
xs = crystal.symmetry( uctbx.unit_cell('30,30,30,109,109,109',
                                   'R3:R' )
xs_new = xs.change_basis( xs.space_group_info().change_of_basis_op_to_reference_setting() )
xs.show_summary()
xs_new.show_summary()




HTH

Peter








Erik Mckee wrote:
Perhaps I am a bit confused here, but doesn't R3 require alpha=beta=90 and
gamma=120?  Or, is this what is meant by the hexagonal setting?

On Wed, 1 Mar 2006, Angela Hoffort wrote:

  
I am trying to sovle MAD data using the PHENIX software. I am using the AutoSol
wizard. My data is integrated in R3. Phenix keeps spitting out the error that
this space group is either unknown or the cell dimensions are inappropriate to
the space group (the are a=b=c=159 and alpha=beta=gamma=109). Is there a glitch
with thi space group or am I doing something wrong. Phaser tends to have the
same problem with this space group and I can not seem to get around it.

If I provide data in a different space group I can get past this problem only to
be confronted with another problem regarding the column labels in my mtz files.
I have six data sets collected. Two for each of three different wavelengths.
Each of the two for a single wavelength is scaled seperately and then merged
together using ccp4. I have taken a lot of effort to make sure that the column
labels do not repeat in these files, yet I continually get column label errors
when I run three mtz files in the AutoSol wizard (one mtz file for each
wavelength). I am getting the same errors in ccp4 as well. There must be
something basic that I am doing wrong with regards to processing my data and
merging the mtzs together.

Thanks you for your help.
Angela

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