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Fluorite structure: Difference between revisions

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{{Short description|Motif in solid state chemistry}}
In [[solid state chemistry]], theThe '''fluorite structure''' refers to a common motif for compounds with the formula MX<sub>2</sub>.<ref>{{Holleman&Wiberg}}</ref><ref>{{Greenwood&Earnshaw2nd}}</ref> The X ions occupy the eight tetrahedral [[interstitial site]]s whereas M ions occupy the regular sites of a [[Cubic crystal system|face-centered cubic]] (FCC) structure. Many compounds, notably the common mineral [[fluorite]] (CaF<sub>2</sub>), adopt this structure.
 
Many compounds with formula M<sub>2</sub>X have an '''antifluorite structure'''. In these the locations of the anions and cations are reversed relative to fluorite (an [[anti-structure]]); the anions occupy the FCC regular sites whereas the cations occupy the tetrahedral interstitial sites. For example, [[magnesium silicide]], Mg<sub>2</sub>Si, 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.<ref name="Costel">{{cite book|url=https://shutterwaves.com/product/structure-of-crystalline-solids/|title=Structure of Crystalline Solids, Imperfections and Defects in Crystals|last1=Rizescu|first1=Costel|last2=Rizescu|first2=Mihaela|publisher=Shutter Waves|year=2018|isbn=978-1-947641-17-4|edition=First|location=Parker, TX|access-date=29 January 2020}}</ref>
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