A general term that implies either the region between the two adjacent layers or the relation between the two adjacent layers (quot Guggenheim et al., 2009). “Interlayer distance” is more precise to describe the distance between the adjacent layers (tetrahedral sheet to tetrahedral sheet, as shown in Fig. 2), and is measured by taking the average of the z coordinate of the basal oxygen plane. The “interlayer displacement” describes the displacement portion or lateral shift from tetrahedral sheet to tetrahedral sheet across the interlayer space. Cf., layer, layer displacement