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

Acta Cryst. (2011). B67, 109-115 (

[Antifluorite] The crystal structures of anticotunnite Rb2S (Pnma) at 0.7 GPa (top) and Rb2SO4 at room conditions (Pnam) (bottom), showing the similarities of both Rb2S arrays. Colour key: Rb-grey, S-yellow, O-tiny-red. [SO4] tetrahedra are olive coloured.

The crystal structures of two new high-pressure phases of Rb2S are reported. Antifluorite Rb2S firstly transforms into an anticotunnite structure below 0.7 GPa and, subsequently, into an Ni2In-type structure at 2.6 GPa. Interestingly, the structures of these phases are identical to the cationic arrays of the two existing polymorphs of the corresponding sulfate, Rb2SO4. Once more, cations do not seem to be 'isolated entities' but they recognize themselves in spite of being surrounded by oxygen atoms.

D. Santamaria-Perez, A. Vegas, C. Muehle and M. Jansen