Si+ is the cation that have small radii and large electrovalence The distance between si and o Si-O: 1.6 A(practical)<1.75 A(theoretic (0.40+1.35)Si4+ is the cation that have small radii and large electrovalence. The distance between Si and O: Si－O : 1.6 Å(practical) < 1.75 Å (theoretic) (0.40+1.35)