An A B_2 type structure is found in

For an $A B_2$ type structure, the equivalent equation at equilibrium is A B_2 $\rightleftharpoons$ A^{2+}+2 B^{-} For $\mathrm{CaF}_2$, the equivalent equation at equilibrium is $\mathrm{CaF}_{2} \rightleftharpoons \mathrm{Ca}^{2+}+2 \mathrm{ F}^{-} \text{. }Therefore \mathrm{CaF}_2 has an$ A B_2$type structure.$