DOE OSTI2020
(Na6B(SeO4)5)2O2 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional and consists of four water molecules and one Na6B(SeO4)5 framework. In the Na6B(SeO4)5 framework, there are three inequivalent Na sites. In the first Na site, Na is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Na–O bond distances ranging from 2.35–2.78 Å. In the second Na site, Na is bonded to six O atoms to form distorted NaO6 octahedra that share a cornercorner with one BO4 tetrahedra, corners with six SeO4 tetrahedra, an edgeedge with one NaO6 octahedra, and an edgeedge with one NaO6 pentagonal pyramid. There are a spread of Na–O bond distances ranging from 2.36–2.79 Å. In the third Na site, Na is bonded to six O atoms to form distorted NaO6 pentagonal pyramids that share corners with six SeO4 tetrahedra and an edgeedge with one NaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.32–2.63 Å. There are two inequivalent B sites. In the first B site, B is bonded to four equivalent O atoms to form BO4 tetrahedra that share corners with four equivalent NaO6 octahedra and corners with four equivalent SeO4 tetrahedra. The corner-sharing octahedral tilt angles are 69°. All B–O bond lengths are 1.48 Å. In the second B site, B is bonded to four equivalent O atoms to form BO4 tetrahedra that share corners with four equivalent SeO4 tetrahedra. All B–O bond lengths are 1.48 Å. There are four inequivalent Se sites. In the first Se site, Se is bonded to four O atoms to form SeO4 tetrahedra that share corners with two equivalent NaO6 octahedra, corners with two equivalent NaO6 pentagonal pyramids, and a cornercorner with one BO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–66°. There are a spread of Se–O bond distances ranging from 1.64–1.78 Å. In the second Se site, Se is bonded to four equivalent O atoms to form SeO4 tetrahedra that share corners with four equivalent NaO6 pentagonal pyramids. All Se–O bond lengths are 1.68 Å. In the third Se site, Se is bonded to four equivalent O atoms to form SeO4 tetrahedra that share corners with four equivalent NaO6 octahedra and corners with four equivalent NaO6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 45°. All Se–O bond lengths are 1.67 Å. In the fourth Se site, Se is bonded to four O atoms to form SeO4 tetrahedra that share corners with three equivalent NaO6 octahedra, corners with two equivalent NaO6 pentagonal pyramids, and a cornercorner with one BO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–69°. There are a spread of Se–O bond distances ranging from 1.65–1.78 Å. There are ten inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to two Na and one Se atom. In the second O site, O is bonded in a bent 150 degrees geometry to one Na and one Se atom. In the third O site, O is bonded in a 3-coordinate geometry to two Na and one Se atom. In the fourth O site, O is bonded to three Na and one Se atom to form distorted edge-sharing ONa3Se tetrahedra. In the fifth O site, O is bonded in a distorted trigonal planar geometry to two Na and one Se atom. In the sixth O site, O is bonded in a distorted trigonal planar geometry to one Na, one B, and one Se atom. In the seventh O site, O is bonded in a distorted trigonal planar geometry to two Na and one Se atom. In the eighth O site, O is bonded in a 4-coordinate geometry to three Na and one Se atom. In the ninth O site, O is bonded in a bent 150 degrees geometry to one Na and one Se atom. In the tenth O site, O is bonded in a 2-coordinate geometry to one Na, one B, and one Se atom.