Contacts() dropped every pair found in image 0 with a nonzero lattice shift ("the identity term
covers the contact"), but that pair is a contact with a translated copy of j, not with j itself:
in P1 no intermolecular repulsion or B-contact restraint was made at all, and in every group the
contacts along a, b and c were missing (MeasureGeometry's clash count with them). Such a pair is
now kept like a symmetry mate's, from the lower atom of the two.
An atom against its own image x -> T x is also met through T^-1 at the same distance (another
operator, or the same one at another lattice shift for a screw), and both were kept: atoms near
a 3-, 4- or 6-fold or a screw axis were repelled twice. For i == j the image first in fractional
coordinates of T x and T^-1 x is kept; an involution is kept once as before.
Test: in P1 two waters 2.4 A apart across a cell face get one repulsion and one B contact (none
before); a water 1.4 A from a 3-fold axis gets one repulsion with its images (two before).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CeEGgpKdfkCTJb3YNMJcu
(cherry picked from commit 0d6e4d0491e655a49d59b709e1398843506d162a)
leonarski_f
2be88e11e3