The Laue condition fixes the component along the beam; a half turn about the spindle negates the
two perpendicular to it and taking -h negates all three, so the composition leaves the beam
component alone and the mate is on the sphere exactly, not nearly. Says that they are separated
by half a turn rather than recorded together precisely because the Ewald sphere is curved - a
near-flat one would excite both at once - and that the positions need only the reciprocal lattice
to be centrosymmetric, Friedel's law entering as the test of a pairing rather than its basis.
Also states the yield: a sweep of S degrees gives S-180 degrees' worth of pairs, so half a turn
gives none and a little over half a turn gives few.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 5
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