FeAs

FeAs, or iron arsenide, is an inorganic binary intermetallic compound consisting of iron and arsenic in a 1:1 ratio. It is primarily of interest in solid-state chemistry and condensed-matter physics as a simple reference system related to iron pnictides.

At ambient pressure, FeAs crystallizes in the orthorhombic MnP-type structure (space group Pnma). The arrangement features zigzag chains of iron atoms coordinated by arsenic and leads to itinerant magnetic behavior. FeAs is metallic and exhibits magnetic ordering at low temperatures; the exact magnetic ground state is sensitive to stoichiometry, defects, and pressure.

Preparation is typically by direct reaction of elemental iron and arsenic at elevated temperature in sealed containers to prevent arsenic vapor release, followed by annealing to improve crystallinity. FeAs is primarily studied in the laboratory and is not produced at industrial scale. It is not a common mineral; trace crystalline samples can be prepared synthetically.

Safety: arsenic compounds are toxic; handling requires appropriate containment, ventilation, and waste disposal.