High-pressure experimental study on Rb2S: antifluorite to Ni2In-type phase transitions.

The high-pressure behaviour of dirubidium sulfide, Rb(2)S, with antifluorite-type structure under room conditions (space group Fm ̄3m) has been studied up to 8 GPa at room temperature using angle-dispersive X-ray powder diffraction in a diamond-anvil cell (DAC). X-ray measurements have allowed us to completely characterize two phase transitions upon compression: (i) to an anticotunnite-type structure (Pnma) at some pressure between 1 bar and 0.7 GPa, and (ii) to a Ni(2)In-type structure (P6(3)/mmc) at 2.