fig2
Figure 2. (A) Basic SiO4 tetrahedra in SiO2 framework [angles (α, φ) and bond lengths d are variable]. (B) Crystal structures of L- and R-quartz. This figure is used with permission from the American Physical Society[24]. (C) Schematic models of a pair of AB4 tetrahedral enantiomers with clockwise or counter-clockwise patterns.
