CaF2, fluorite

Tetrahedral CaF2 (fluorite) SrCl2 (fluorite). Br04, FBr03, IO4-... 

Ca F F CaF2 (fluorite) F m3m BaCl2, ThO2, TiH2, Li2O, Be2C, Mg2Sn... 

Figure B.6. Structures built from stacking tetrahedra ZnS, wurtzite, 2-2PT ZnS, zinc blends, 3-2PT and CaF2, fluorite 3-d PTT.

Many ionic compounds of AX2 stoichiometry possess the CaF2 (fluorite), or Na20 (antifluorite) structures shown in Figure 3.15. Fluorite is similar to CsCl, but with every other eight coordinate cation removed. Each fluoride anion is tetrahedrally coordinated by calcium ions. This structure is adopted by several fluorides and oxides. In the antifluorite structure, the coordination numbers are the inverse. Most oxides and other chalcogenides of the alkali metals (e.g. Na2Se, K2Se) possess the antifluorite structure, but so do some more covalent compounds, such as the silicides of Mg, Ge, Sn, and Pb. 

Equation (33) states that the ratio of intensities from a peak from phase A and one from the standard is a linear function of the weight fraction of phase A. A calibration curve can be set up containing known concentrations of A and a constant concentration of a suitable standard phase. Then the concentration of phase A in the unknown is obtained by measuring Ia/L in which the same amount of the standard was added to the unknown as was used to prepare the standard curve. Good standards to use are a - AI2 O3, a synthetic corundum marketed as Linde A and CaF2, fluorite. 

Na, metal Cdl2, layered structure octahedral site, 6-coordinate Ga-doped Si, extrinsic semiconductor Na2S, antifluorite structure perovskite, double oxide CaF2, fluorite structure GaAs, intrinsic semiconductor wurtzite and zinc blende, polymorphs Sn02, cassiterite. 

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