A crystal lattice spacing is the repeated distance between parallel planes, and this lesson checks only that geometry, not full 3-D protein structure or phase retrieval. The simplified training crystal has plane spacing d = 4 m exactly for the stated toy lattice ledger; real crystals have finite domains, disorder, orientation spread, detector calibration, and measurement uncertainty.
A simplified crystal diagram uses repeated planes to represent a measured spacing. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A crystal model repeats a spacing
Parallel planes mark a repeating distance in this simplified crystal model.
parallel planes set the repeat distance
The repeat distance is exact
The spacing from one drawn plane to the next is 4 meters. Real protein crystals are three-dimensional and need phase retrieval; this lesson only checks spacing geometry.
d=4m
Repeated plane coordinates keep the same spacing
The coordinate differences are checked between adjacent drawn planes. Each repeated step is the same spacing.