2,684
edits
Old way of Space group determination: Difference between revisions
Old way of Space group determination (view source)
Revision as of 22:48, 6 January 2013
, 6 January 2013small fixes
(small fixes) |
|||
| Line 20: | Line 20: | ||
** ''modify or insert UNIT_CELL_PARAMETERS= according to table, but make them obey space group requirements (e.g. orthorhombic: all angles 90°, tetragonal and trigonal: a=b, and so on).'' | ** ''modify or insert UNIT_CELL_PARAMETERS= according to table, but make them obey space group requirements (e.g. orthorhombic: all angles 90°, tetragonal and trigonal: a=b, and so on).'' | ||
** ''run XDS with JOB=CORRECT. Inspect [[CORRECT.LP]] and note R-factors, I/sigma and a and b modifiers of standard deviations'' | ** ''run XDS with JOB=CORRECT. Inspect [[CORRECT.LP]] and note R-factors, I/sigma and a and b modifiers of standard deviations'' | ||
** ''for many Bravais types (defined at [http://www.iucr.org/iucr-top/cif/cifdic_html/2/cif_sym.dic/Ispace_group.Bravais_type.html]), there are several possible point groups ( | ** ''for many Bravais types (defined at [http://www.iucr.org/iucr-top/cif/cifdic_html/2/cif_sym.dic/Ispace_group.Bravais_type.html]), there are several possible point groups (tP and tI: 4, 422; hP: 3, 6, 312, 321, 622; hR: 3, 32; cP, cF and cI: 23 and 432) and thus several possible space groups. In these cases, each point group has to be tested: the SPACE_GROUP_NUMBER has to be changed to one of those consistent with the point group, and the CORRECT step re-run.'' | ||
* ''repeat for each possible lattice character'' | * ''repeat for each possible lattice character'' | ||
* ''finally decide on the correct Bravais lattice and point group by comparing R-factors (in particular R<sub>meas</sub>), and, from there, come up with possible space groups by looking at the table of systematic absences along the h,0,0 0,k,0 and 0,0,l axes of the diffraction pattern.'' | * ''finally decide on the correct Bravais lattice and point group by comparing R-factors (in particular R<sub>meas</sub>), and, from there, come up with possible space groups by looking at the table of systematic absences along the h,0,0 0,k,0 and 0,0,l axes of the diffraction pattern.'' | ||
| Line 30: | Line 30: | ||
== Example == | == Example == | ||
old versions of XDS produced a list sorted by Lattice Character number: | |||
LATTICE- BRAVAIS- QUALITY UNIT CELL CONSTANTS (ANGSTROEM & DEGREES) REINDEXING CARD (CORRECT) | LATTICE- BRAVAIS- QUALITY UNIT CELL CONSTANTS (ANGSTROEM & DEGREES) REINDEXING CARD (CORRECT) | ||
| Line 79: | Line 79: | ||
43 mI 999.0 219.4 537.2 164.1 107.7 138.4 66.0 -1 1 0 0 -1 1 -2 0 0 -1 0 0 | 43 mI 999.0 219.4 537.2 164.1 107.7 138.4 66.0 -1 1 0 0 -1 1 -2 0 0 -1 0 0 | ||
44 aP 0.0 145.8 164.1 245.4 90.1 90.0 90.1 -1 0 0 0 0 1 0 0 0 0 -1 0 | 44 aP 0.0 145.8 164.1 245.4 90.1 90.0 90.1 -1 0 0 0 0 1 0 0 0 0 -1 0 | ||
The top 12 sorted by "Quality of Fit (QoF)" are: | |||
44 aP 0.0 145.8 164.1 245.4 90.1 90.0 90.1 -1 0 0 0 0 1 0 0 0 0 -1 0 | 44 aP 0.0 145.8 164.1 245.4 90.1 90.0 90.1 -1 0 0 0 0 1 0 0 0 0 -1 0 | ||
31 aP 0.3 145.8 164.1 245.4 89.9 90.0 89.9 1 0 0 0 0 1 0 0 0 0 1 0 | 31 aP 0.3 145.8 164.1 245.4 89.9 90.0 89.9 1 0 0 0 0 1 0 0 0 0 1 0 | ||