1 Answers
In solid state chemistry, the fluorite structure refers to a common motif for compounds with the formula MX2. The X ions occupy the eight tetrahedral interstitial sites whereas M ions occupy the regular sites of a face-centered cubic structure. Many compounds, notably the common mineral fluorite , adopt this structure.
Many compounds with formula M2X have an antifluorite structure. In these the locations of the anions and cations are reversed relative to fluorite ; the anions occupy the FCC regular sites whereas the cations occupy the tetrahedral interstitial sites. For example, Magnesium silicide, Mg2Si, has a lattice parameter of 6.338 Å with magnesium cations occupying the tetrahedral interstitial sites, in which each silicide anion is surrounded by eight magnesium cations and each magnesium cation is surrounded by four silicide anions in a tetrahedral fashion.
The fluorite structure of calcium fluoride CaF2.
The antifluorite structure of magnesium silicide Mg2Si.