Whopes
Hey I just met you, and this is crazy, but heres my number, so call me maybe. Pointless scores all the possible Laue groups consistent with the crystal class, which is based on cell dimension restraints. It does this by matching potential symmetry equivalent reflections. For chiral systems, the Laue group uniquely implies the point group. It then checks sets of reflections which may be systematically absent to suggest a possible spacegroup. There is also a check for lattice centering, ie a check for whole classes of reflections having essentially zero intensity, including a check for obverse/inverse twinning in rhombohedral systems.
Given test data comprising unmerged observations (file(s) HKLIN, XDSIN or SCAIN), the program looks for possible symmetry based on the unit cell in order to determine the Laue group, ie the symmetry of the diffraction pattern. It then examines axial reflections (and zones for non-chiral crystals) to look for systematic absences to determine the space group.
Given a test dataset, merged or unmerged (file(s) HKLIN), and a merged or unmerged reference dataset in a known space group (file HKLREF), the program tests all possible alternative indexing schemes of the test dataset to find which one best matches the reference set. Alternative indexing schemes arise in high symmetry space groups when the lattice symmetry is higher than the point group symmetry (eg for trigonal space groups), but may also arise in any space group from special relationships between cell parameters (eg an orthorhombic cell with a=b or more complicated examples involving cell diagonals).
It is occasionally (though rarely) possible to misindex the diffraction pattern by (say) +-1, usually on a long axis approximately parallel to the rotation axis. In this case, the centre of symmetry of the diffraction pattern is apparently not at hkl 0,0,0 as it should be. The CENTRE option does an R-factor search for the correct centre. Note that if the Laue group symmetry is
Given test data comprising unmerged observations (file(s) HKLIN, XDSIN or SCAIN), the program looks for possible symmetry based on the unit cell in order to determine the Laue group, ie the symmetry of the diffraction pattern. It then examines axial reflections (and zones for non-chiral crystals) to look for systematic absences to determine the space group.
Given a test dataset, merged or unmerged (file(s) HKLIN), and a merged or unmerged reference dataset in a known space group (file HKLREF), the program tests all possible alternative indexing schemes of the test dataset to find which one best matches the reference set. Alternative indexing schemes arise in high symmetry space groups when the lattice symmetry is higher than the point group symmetry (eg for trigonal space groups), but may also arise in any space group from special relationships between cell parameters (eg an orthorhombic cell with a=b or more complicated examples involving cell diagonals).
It is occasionally (though rarely) possible to misindex the diffraction pattern by (say) +-1, usually on a long axis approximately parallel to the rotation axis. In this case, the centre of symmetry of the diffraction pattern is apparently not at hkl 0,0,0 as it should be. The CENTRE option does an R-factor search for the correct centre. Note that if the Laue group symmetry is