Tags: Chemical Compound, Chemical Substance.
Iron(II) selenide refers to a number of inorganic compounds of ferrous iron and selenide (Se2-). The phase diagram of the system Fe-Se reveals the existence of several non-stoichiometric phases between ~49 at. % Se and ~53 at. % Fe and temperatures up to ~450 °C. The low temperature stable phases are the tetragonal PbO-structure (P4/nmm) β-Fe1-xSe and α-Fe7Se8. The high temperature phase is the hexagonal NiAs structure (P63/mmc) δ-Fe1-xSe.