Germanium(cF136): A new crystalline modification of germanium with the porous clathrate-II structure

(Figure Presented) Homoatomic Zintl ions (for example, [Ge ₉]^4-; see picture, left) have long been discussed as precursors for the formation of more complicated structures. The characterization of "□₂₄Ge₁₃₆" with the (unfilled) clathrate-II structure (right; orange, gray, yellow: pentagonal dodecahedra, pink: hexakaidecahedra) and other porous germanium-based materials supports this hypothesis.