Ionic Crystal Structures

Rock Salt (AX)

1:1 stoichiometry

A and X are 6 coordinate

face centered cubic lattice

octahedral holes

CsCl Structure (AX)

1:1 stoichiometry

A and X are 8 coordinate

primitive cubic lattice

octahedral holes

often large cation with small anion

Zinc Blende Structure (AX)
1:1 stoichiometry
A and X are 4 coordinate
FCC lattice
tetrahedral holes
important for semi conductors
looks like diamond but with mix of ions

Wurtzite Structure (AX)
1:1 stoichiometry
A and X are 4 coordinate
hexagonal close packed lattice
tetrahedral holes

Fluorite Structure (A2X)
Corners- cation
1:2 stoichiometry
A is 8 coordinate, X is 4 coordinate
FCC lattice
X in tetrahedral holes of A lattice
common compounds: halides + alkali earth metals

Anti-fluorite Structure (AX2)
Corners- anion
2:1 stoichiometry
A is 4 coordinate, X is 8 coordinate
FCC latice
A in tetrahedral holes of X lattice
common compounds: oxides (Li2O, Na2O, etc)

Rutile Structure (AX2)
1:2 stoichiometry
A is 6 coordinate, X is 3 coordinate
body centered tetragonal

Anatase Structure-
polymorph of rutile

Perovskite Structure (ABX3)
1:1:3 stoichiometry
A is 12 coordinate, B is 6 coordinate
X is 6 coordinate (4 with A, 2 with B)
Primitive cubic lattice
A in central octahedral hole w/in B lattice
A cation has a lower oxidation state than B cation