Non-Sohncke candidates were enumerated only when their PROPER rotations equalled the measured
point group's, which only centrosymmetric groups satisfy. Groups without a centre (Pc, Pna2_1,
I-42d, I4_1md, Fdd2, P-42_1c, I-43d) were never candidates: where a centrosymmetric group shares
their absences rugnux wrote it silently (Pc -> P2/c), and where none does the dead glide zone was
dropped and a Sohncke subgroup written (KDP-type I-42d data -> I4_122).
- Enumerate non-Sohncke groups by Laue class. The Sohncke-signature dedup, CellHostsRotations and
the glide-evidence bar are unchanged. Groups with identical absences in the same Laue class are
scored once and carried as `same_absences`; a selected candidate brings them into
`alternatives`.
- Convention for which twin is written: the centrosymmetric one where it exists (missed centres are
the common error, Baur & Kassner 1992), otherwise the lowest-numbered (I4_1md over I-42d).
- The centrosymmetric default gives way only when, on the general reflections of the Laue class of
the final merge, <|L|>, <|E^2-1|> and N(0.1), each calibrated against acentric/centric intensities
simulated with the reflections' own sigmas (fixed-seed mt19937_64, own deviate transforms), read
acentric (L f <= 0.3, others <= 0.5), every f lies in [-0.3, 1.3], the always-centric control reads
centric (f >= 0.5), and the lattice excludes twinning (gemmi Le Page metric admits no rotation
beyond the Laue class, no TWIN_DOMAIN leftover lattice). Then the group is switched and re-merged.
- Report: SPACE_GROUP_CENTRE (IMPLIED_BY_ABSENCES / ABSENT_BY_ABSENCES / NOT_DETERMINED /
ABSENT_BY_STATISTICS), CENTRE_TWINNING_EXCLUDED, CENTRE_STATISTICS_* on every searched run, and
prose for the absence-equivalent alternatives.
Battery (targeted): all 14 small-molecule sets vs 58a4bf (smt-all, kdp-all): every group
unchanged except kdp_x10sa_20keV I 41 2 2 -> I 41 m d with I -4 2 d as the alternative; dnba stays
C 1 2/c 1, now NOT_DETERMINED with C 1 c 1 listed (statistics read centric, f 0.96-1.24). The
P2_1/c, Pbca and Ia-3d sets read IMPLIED_BY_ABSENCES with no alternative.
Protein panel (19 sets, twinned panel + controls, run glide-prot): every space group equals the
rc174-all base (3r6o re-run with the base binary: I 41 2 2 both); no SPACE_GROUP_CENTRE on any.
Twinned proteins read the centre statistics NOT_APPLICABLE (L f -0.3 to -1.7) or ACENTRIC.
Private subset (8 sets): 8/8 groups unchanged vs 58a4bf.
The glide-zone evidence scan over battery 3 (every non-Sohncke group of each run's Laue class,
centrosymmetric or not) peaks at 0.69 nats/reflection on proteins against the 2.0 bar.
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
60b7fb86fa
