Fluorite Structure Cl

The fluorite structure (Cap2) has the formula AX2 (A is the cation and X the anion). We now must have twice the number of anions than cations. The structure works out to be fee with the cations on the fee sites and the anions occupying all of the tetrahedral positions (space 

Fluorite structure, t)rpical for AX2 compounds, places the divalent A cations on the fee sites and the monovalent X anions on all of the tetrahedral sites in order to balance the charge. Each anion is coordinated with one corner and three face cations. Each cation is coordinated by eight anions. 

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