Thulium monoselenide

Thulium monoselenide is a mixed valence compound of selenium and thulium with the chemical formula TmSe.

Preparation
Thulium monoselenide can be prepared by directly reacting thulium and selenium:


 * Tm + Se -> TmSe

Properties
Thulium monoselenide forms reddish-brown cubic crystals, space group Fm$\overline{3}$m, unit cell parameters a = 0.5640 nm, Z = 4, and a structure similar to that of sodium chloride.

The compound melts congruently at 2060 °C, and at 1100 °C and 1730 °C, phase transitions occur in the compound. The Néel temperature of thulium monoselenide is 1.85–2.8 K.