Where the first pass recognises two twin domains on their coincidence lattice (reticular
merohedry, index n = 2 or 3) and adopts the stronger domain's cell, the 1/n of that domain's
reflections that lie on the other domain's lattice too carry both domains' intensity. The step
now records the overlap as a lattice vector t of the standing cell (h . t divisible by n), the
rotation result carries it, and the per-image integration drops those reflections. t is a
real-space vector, so it holds through every later change of basis; it is read in sixths so a
centred conventional cell (F, I, C, R) is exact. Each unique reflection keeps its equivalents
that the other domain does not overlap; only those whose every equivalent is overlapped are lost.
The two-pass quality guard compared signal counts between a header pass that integrated
everything and a refined pass that left the overlap out, and sent the run back to the
composite lattice. A pass that left an overlap of index n out now has its counts taken up by
n/(n-1), and its axial rows are not compared with a pass that did not.
Nothing changes where the step does not fire: the field stays empty, the factor is 1.
Measured (merging the existing outputs with and without the class H.(111) = 0 mod 3, against
removing a random third): spinel-twinned F-cubic private set R_meas 25.5 -> 14.3% (random
26.7%), insu_I_x06da_low_isa 24.1 -> 16.6% (random 24.2%). With this change, end to end:
- insu_I_x06da_low_isa: I23, R_meas 24.0 -> 12.7%, ISa 5.2 -> 28.8, CC1/2 0.997 -> 1.000,
completeness 99.8 -> 95.7%, d 1.45 -> 1.47 A, model R-free 0.260 -> 0.246.
- private F-cubic twin: F432, R_meas 25.5 -> 6.3%, ISa 3.9 -> 20.4, completeness 100 -> 93%,
d 3.23 -> 3.77 A (XDS reference 4.0). 432 now passes the added-operator gate on the
all-observation merge (contrast 0.75, bound 0.72) instead of being refused there (0.62) and
rescued by the twin-immune zone.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SVmAWnzCmRKAXVUCdc4iNi
leonarski_fandClaude Opus 5.5
e2b0e7dfb3