Materials Data on K2U2O7 by Materials Project

K2U2O7 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six O2- atoms to form KO6 octahedra that share corners with four equivalent UO6 octahedra and edges with six KO6 octahedra. The corner-sharing octahedra tilt angles range from 55–58°. There are three shorter (2.71 Å) and three longer (2.78 Å) K–O bond lengths. In the second K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with two equivalent UO6 octahedra and edges with six KO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There are a spread of K–O bond distances ranging from 2.80–2.82 Å. There are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of U–O bond distances ranging from 1.87–2.54 Å. In the second U6+ site, U6+ is bonded to six O2- atoms to form distorted UO6 octahedra that share corners with two equivalent UO6 octahedra and corners with six KO6 octahedra. The corner-sharing octahedra tilt angles range from 40–60°. There are a spread of U–O bond distances ranging from 1.91–2.29 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three K1+ and one U6+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three K1+ and one U6+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three K1+ and one U6+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to three K1+ and one U6+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to three U6+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to three U6+ atoms. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to three U6+ atoms.