RESULT-CHANGING.
A tetragonal crystal in 4 twinned ~0.3 by k,h,-l (3r6o, I4_1) was merged in I4_122. Since the
beam-stop fix both search arms passed 422 (H ratio 1.51 < 1.85); before it the Lorentz-filtered
arm refused at 2.13x and was overridden by the all-observation arm. Either way the twin-immune
zone - the one reading a twin cannot fake - was never asked: the Stage A zone gate skipped any
candidate that holds every rotation of its lattice, on the argument that no twin law exists for
such a group. But the subgroup's twin law is one of the candidate's own operators, so the
holohedral promotion is exactly the commonest merohedral-twin case (4 -> 422, 3 -> 32 on a
rhombohedral lattice, 321 -> 622), and the L-test-under-merge gate leaves such a twin in the
higher group by design. The gate now runs whenever the P1 merge reads twinned
(<|L|> in [0.375, 0.44)), holohedral or not. 3r6o reads 422 over 4 at -58 nats (acentric).
With 422 refused, the all-observation arm took 222 over 4: the same-order tie-break credits a
group's axial two-folds with the screw evidence of their rows, and on a body-centred crystal
the I centring kills the odd class of every principal row (30 nats each), so a 222 of the real
2-fold plus two twin laws beat the crystal's own 4. Rows whose odd class a centring extinguishes
are no longer counted where the merge reads that centring on its general reflections (the
centring class at < 0.25 of the rest's mean E^2; measured 0.11-0.13 for I on 3r6o, 0.97-1.00
for the absent centrings).
Changed (CPU screen of 53 sets against the kept rc175 run 20261016-0057, plus 3r6o):
- 3r6o: I4_122 -> I4_1 (deposited I4_1), TWINNING INDICATED, twin law h,-k,-l ~0.32;
ISa 4.15 -> 7.77, R_meas 0.218 -> 0.146, CC1/2 0.989 -> 0.993.
- 8c3e: P622 -> P321 with P3_121 | P3_221 as alternatives, screw on c undetermined (deposited
P3_121, twinned): 622 refused at -70.8 nats; ISa 5.69 -> 6.91.
Unchanged: 3mc4, 5j23, 6toc, 6oww, 6iu5/6/9, 2wnn, 2xfw, 4bwl, 5ebi, 2wnq, 6vww, 7k1l, 6pxb,
8xte, 8xtg, 9i80, 5uth, 6h5t, 8k1g, 6moj, 7kcn, 5vml, 3p85, 7rji, 8xtf, 9h0q, 7l84, 6v2r, 7t5t,
5m17, 6p8p, 3meb, 5cc8, 9lxl, 8v4j, 6zqr, 9fcf, 5src, 11if, cuhf2, lyso_x06da_ref,
lyso_x10sa_90deg_1, thau_x10sa_16keV, thau_bl1a_6p5keV, insu_H_x06da_twin/notwin,
insu_I_x06da_ref, cytc_x06da_1, myob_x06da_split, kdp_x10sa_20keV (space group identical,
ISa within run noise; 7l84/5src/11if differ only by the model-adopted enantiomorph label).
Test: a body-centred 4 twinned at 0.45, given its cell, stays in 4 (222 without the centring
rule). [SearchSpaceGroup], [twinning], [twin] pass.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PXc1zD1yxHqaR1DGdCTHL4
leonarski_fandClaude Opus 5.5
7c1befd484