Materials Data on MgU8Se17 by Materials Project

MgU8Se17 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Mg2+ is bonded in an octahedral geometry to six Se2- atoms. There are two shorter (2.54 Å) and four longer (2.64 Å) Mg–Se bond lengths. There are three inequivalent U4+ sites. In the first U4+ site, U4+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of U–Se bond distances ranging from 2.89–3.04 Å. In the second U4+ site, U4+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of U–Se bond distances ranging from 2.84–2.95 Å. In the third U4+ site, U4+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of U–Se bond distances ranging from 2.79–3.11 Å. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four U4+ atoms. In the second Se2- site, Se2- is bonded to six U4+ atoms to form a mixture of face and corner-sharing SeU6 octahedra. In the third Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four U4+ atoms. In the fourth Se2- site, Se2- is bonded to one Mg2+ and three U4+ atoms to form distorted SeMgU3 tetrahedra that share a cornercorner with one SeU6 octahedra, corners with five equivalent SeMgU3 tetrahedra, a cornercorner with one SeMgU3 trigonal pyramid, edges with two equivalent SeMgU3 tetrahedra, and an edgeedge with one SeMgU3 trigonal pyramid. The corner-sharing octahedral tilt angles are 53°. In the fifth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four U4+ atoms. In the sixth Se2- site, Se2- is bonded to one Mg2+ and three U4+ atoms to form distorted SeMgU3 trigonal pyramids that share corners with two equivalent SeMgU3 tetrahedra, a cornercorner with one SeMgU3 trigonal pyramid, edges with two equivalent SeMgU3 tetrahedra, and a faceface with one SeU6 octahedra. In the seventh Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to four U4+ atoms.