Fluorite (CaF2)

Stoichiometry = AX2

Space Group = Fm3m (225)

a = ~[4.3-8.2 angstroms]

Atomic Positions
        Ca   4a    0, 0, 0
        F     8c    0.25, 0.25, 0.25

Coordination Numbers/Geometry
        Ca    CN=8    Cubic coordination
        F      CN=4    Tetrahedral coordination

Representative Compounds*
        Intermetallics (26) - (i.e. PtGa2, SnMg2, AuIn2)
        Oxides (15) - (i.e. CeO2, TbO2, UO2)
        Halides (18) - (i.e. CaF2, EuF2, HgF2)
        Hydrides (13) - (i.e. CeH2, LuH2, NbH2)
        Nitrides (4) - (i.e. UN2)

*The numbers in parentheses are the number of compounds of each type found
in "Structure and Properties of Inorganic Solids" by Francis Galasso, Pergammon Press
(1970).
 


 
 

The fluorite structure can be generated by starting with a FCC lattice of Ca and
filling all of the tetrahedral holes with F.

It is generally easy to incorporate some vacancies on the anion sublattice, some of
these compounds, such as Zr1-xYxO2-x/2 (otherwise known as yttrium stabilized
zirconia), find widspread use as oxygen ion conductors.

The so-called antifluorite structure is analogous to the fluorite structure, with the
cations and anions reversed (i.e. Na2O).