DOE OSTI2020
U6Si11O crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. U+3.67+ is bonded to eleven Si+1.82- and one O2- atom to form a mixture of face and edge-sharing USi11O cuboctahedra. There are a spread of U–Si bond distances ranging from 2.95–3.05 Å. The U–O bond length is 2.96 Å. There are five inequivalent Si+1.82- sites. In the first Si+1.82- site, Si+1.82- is bonded in a 9-coordinate geometry to six equivalent U+3.67+ and three equivalent Si+1.82- atoms. All Si–Si bond lengths are 2.31 Å. In the second Si+1.82- site, Si+1.82- is bonded in a 9-coordinate geometry to six equivalent U+3.67+ and three equivalent Si+1.82- atoms. All Si–Si bond lengths are 2.33 Å. In the third Si+1.82- site, Si+1.82- is bonded in a single-bond geometry to six equivalent U+3.67+, two equivalent Si+1.82-, and one O2- atom. Both Si–Si bond lengths are 2.35 Å. The Si–O bond length is 2.25 Å. In the fourth Si+1.82- site, Si+1.82- is bonded in a 9-coordinate geometry to six equivalent U+3.67+ and three equivalent Si+1.82- atoms. In the fifth Si+1.82- site, Si+1.82- is bonded in a 9-coordinate geometry to six equivalent U+3.67+ and three Si+1.82- atoms. O2- is bonded in a distorted trigonal planar geometry to six equivalent U+3.67+ and three equivalent Si+1.82- atoms.