Cerium(III) fluoride (or cerium trifluoride), CeF₃, is an ionic compound of the rare earth metal

cerium Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the +3 o ...

and

fluorine Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reacti ...

. It appears as a mineral in the form of fluocerite-(Ce) - a very rare mineral species related mainly to

pegmatites A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic comp ...

and rarely to oxidation zones of some

polymetallic In chemistry or mining, polymetal or polymetallic is a substance composed of a combination of different metals. When the substance contains only two metals the term ''bimetal'' (''bimetallic'') is sometimes preferred. A (or ') is an ore that is ...

ore deposits. CeF₃ may be used as a

Faraday rotator A Faraday rotator is a polarization rotator based on the Faraday effect, a magneto-optic effect involving transmission of light through a material when a longitudinal static magnetic field is present. The state of polarization (such as the axis of ...

material in the visible, near-infrared and mid-infrared spectral range.

Structure

The

crystal structure In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...

of cerium(III) fluoride is described as the or tysonite structure. It contains 9-coordinate cerium ions that adopt an approximately

tricapped trigonal prismatic In chemistry, the tricapped trigonal prismatic molecular geometry describes the shape of compounds where nine atoms, groups of atoms, or ligands are arranged around a central atom, defining the vertices of a triaugmented triangular prism (a trigo ...

coordination geometry The term coordination geometry is used in a number of related fields of chemistry and solid state chemistry/physics. Molecules The coordination geometry of an atom is the geometrical pattern formed by atoms around the central atom. Inorganic coo ...

, although it can be considered 11-coordinate if two more distant fluorides are considered part of the cerium coordination environment. The three crystallographically independent fluoride ions are 3-coordinate and range in geometry from

trigonal planar In chemistry, trigonal planar is a molecular geometry model with one atom at the center and three atoms at the corners of an equilateral triangle, called peripheral atoms, all in one plane. In an ideal trigonal planar species, all three ligands a ...

pyramidal A pyramid (from el, πυραμίς ') is a structure whose outer surfaces are triangular and converge to a single step at the top, making the shape roughly a pyramid in the geometric sense. The base of a pyramid can be trilateral, quadrilater ...

References

Cerium(III) compounds Fluorides Lanthanide halides {{inorganic-compound-stub