The non-reference settings of the adopted point group were offered only when the cell hosted their
rotations to within ~0.1 deg, while the reference settings - which hold the very same rotations -
were offered without asking. A cell refined free after integration a few tenths of a degree off 90
therefore lost every setting but the reference one. On an orthorhombic set whose measured screws
lie on a and c and whose b row was never recorded, that left P2(1)2(1)2(1) as the only candidate
covering both screws, and it was reported as determined. With P 21 2 21 offered, the two tie, the
b-axis screw is reported as undetermined, and the model check uses the setting the data describe.
The point-group stage still asks the cell whether a rotation set it adds is hosted; only the
setting enumeration within an already chosen set stops asking.
Validation: myob/cytc/thau x10sa p.mtz byte-identical (GPU); 7mzt fail -> unscored (b screw
undetermined, P 21 21 21 or P 21 2 21); 5cc8 unchanged; [SearchSpaceGroup] 23 cases pass incl. a
new section with a cell 0.2-0.3 deg off 90.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K5K8jvPPbmCrbqnWkddTuB
leonarski_fandClaude Opus 5.5
da5ef0c503