Before revision: Interstitial atoms (blue) occupy some of the spaces within a lattice of larger atoms (red) Interstitial defects are a variety of crystallographic defects where atoms assume a normally unoccupied site in the crystal structure.
After revision: Interstitial atoms (blue) occupy some of the spaces within a lattice of larger atoms (red) An interstitial defect is a type of point crystallographic defect where an atom of the same or of a different type, occupies a normally unoccupied site in the crystal structure.