Fluorite 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 Ca 2 + ions are eight-coordinate, being centered in a cube of eight F − ions. Each F − is coordinated to four Ca 2 + 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 d yz and d z 2 squared. The molecule in linear when they are in the d z 2 orbitals the molecule is also the most stable in this shape. When the electrons are in the d yz 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).