Cs2Pt: A Platinide(‐II) Exhibiting Complete Charge Separation

Relatively ionic: The new platinide Cs2Pt is dark red and transparent. The calculated band structure shows a complete transfer of the valence electrons from cesium to platinum, which exists as a Pt2− ion. This result is further experimental evidence for a relativistic lowering of the 6s orbital energy. The crystal structure, a Ni2In structure type (see picture; Cs yellow, Pt blue), is a high-pressure polymorph of the CaF2 structure. Hence, according to the pressure-homologue rule Cs2Pt can be considered as a homologue of the alkali-metal chalcogenides.