5.5.4: Structure - Fluorite and Antifluorite
- Page ID
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Calcium Fluoride is a solid and forms a cube like structure that is centralized around the calcium molecules. The crystal lattice structure that Calcium Fluoride is also known as the fluorite structure (Figure \(\PageIndex{1}\)) where the Ca2+ ions are eight-coordinate, being centered in a cube of eight F− ions. Each F− is coordinated to four Ca2+ in the shape of a tetrahedron.
When Calcium Fluoride is in a single molecule it forms a Quasilinear structure. Quasilinear means the molecule resonates between a linear shape and a bent shape.Calcium Fluoride is a polyatomic molecule that contains one calcium molecule and two fluoride molecules. Calcium Fluoride is a quasilinear molecule the bonds are created from the single electrons of calcium and the single electron from fluoride. \(\ce{CaF2}\) has its electrons contained with in the 3d orbitals and are able to move between dyz and dz2 squared. The molecule in linear when they are in the dz2 orbitals the molecule is also the most stable in this shape. When the electrons are in the dyz orbitals the molecule becomes bent. The molecule resonates between these two shapes making it quasilinear.
Antifluorite
Antifluorite is a mineral with a crystal structure identical with that of fluorite but with the positions of the cations and anions reversed (Figure \(\PageIndex{2}\)).
The same crystal structure is found in numerous ionic compounds with formula AB2, such as ceria (CeO2), zirconia (cubic ZrO2), uranium dioxide (UO2). In the corresponding anti-structure, called the antifluorite structure, anions and cations are swapped, such as beryllium carbide (Be2C) or lithium oxide (Li2O), potassium sulfate (K2SO4).
Contributors and Attributions
- en.Wikipedia.org/wiki/Anti-structure