This constant represents the lattice spacing d₂₂₀ (expressed in meters) of the element silicon (Si) based on its diamond cubic crystal structure.

Notes

This constant is specified with a standard uncertainty (standard deviation) of:  0.0000032 E-12 m

For over fifty years highly pure silicon crystals with an almost perfect lattice have been produced and this constant represents the empirical measurement of the lattice spacing in this crystal Silicon.