Interplanar spacing
From Online Dictionary of Crystallography
Distance interplanaire (Fr); Distanza interplanare (It); 面間距離 (Ja).
The interplanar spacing or interplanar distance is the perpendicular distance between two successive planes on a family (hkl). It is commonly indicated as dhkl and corresponds to the reciprocal of the length of the corresponding vector in reciprocal space:
where G* is the metric tensor in the reciprocal space and T stands for transposed vector.