Stoichiometry = AX
Space Group = Fm3m (225)
A 4a 0, 0, 0
X 4b ½, ½, ½
A CN=6 Octahedral coordination
X CN=6 Octahedral coordination
Intermetallics (55) - (i.e. PY)
Oxides (22) - (i.e. MgO)
Halides (21) - (i.e. LiF)
Carbides (10) - (i.e. ZrC)
Borides (3) - (ZrB, PuB, HfB)
Hydrides (5) - (i.e. PdH)
Nitrides (25) - (i.e. ZrN)
Sulfides, Selenides and Tellurides (63) - (i.e. SrS)
*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 rock salt structure is a highly symmetric one that can be described in many different ways:
(1) The structure can be generated by putting both Na and Cl on the same sites in a FCC lattice, then shift one of the two networks (Na or Cl) by (½, 0, 0).
(2) The structure can also be described as a cubic close packing of anions, with all of the octahedral holes filled by cations (or vice versa). This description can clearly be seen in the left hand figure above.
(3) From a polyhedral representation the NaCl6 octahedra are seen to share all 8 edges with neighboring octahedra, as seen in the right hand figure above.
The high symmetry and efficient packing of this structure is favored by a wide variety of materials including:
The pyrite, FeS2 (fools gold) and CaC2 structures are derived from the NaCl structure by substituting linear S2 and C2 units respectively onto the chloride lattice sites. Orientation of the S2 and C2 units is different however, giving rise to different space groups for each (FeS2 = Pa3, CaC2 = I4/mmm).