Anti-structure
In crystallography, an anti-structure is obtained from a salt structure by exchanging anion and cation positions.
For instance, calcium fluoride, CaF2, crystallizes in a cubic motif called the fluorite structure. The same crystal structure is found in numerous ionic compounds with formula AB2, such as ceria, zirconia, uranium dioxide. In the corresponding anti-structure, called the antifluorite structure, anions and cations are swapped, such as beryllium carbide or lithium oxide, potassium sulfate.
Other anti-structures include: