Materials Data on Na6Se2O9 by Materials Project
Na6Se2O9 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are eight inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with three NaO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, corners with three SeO4 tetrahedra, edges with two NaO6 octahedra, an edgeedge with one NaO6 pentagonal pyramid, and a faceface with one SeO6 octahedra. The corner-sharing octahedra tilt angles range from 8–61°. There are a spread of Na–O bond distances ranging from 2.36–2.48 Å. In the second Na1+ site, Na1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.19–2.95 Å. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–2.82 Å. In the fourth Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with three NaO6 octahedra, corners with two equivalent NaO6 pentagonal pyramids, corners with three SeO4 tetrahedra, edges with two NaO6 octahedra, and a faceface with one SeO6 octahedra. The corner-sharing octahedra tilt angles range from 8–61°. There are a spread of Na–O bond distances ranging from 2.36–2.51 Å. In the fifth Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.14–3.00 Å. In the sixth Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.34–2.67 Å. In the seventh Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share corners with three NaO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, corners with three SeO4 tetrahedra, an edgeedge with one NaO6 octahedra, a faceface with one SeO6 octahedra, and a faceface with one NaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 8–49°. There are a spread of Na–O bond distances ranging from 2.39–2.55 Å. In the eighth Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.24–2.91 Å. There are four inequivalent Se6+ sites. In the first Se6+ site, Se6+ is bonded to four O2- atoms to form SeO4 tetrahedra that share corners with four NaO6 octahedra and corners with two equivalent NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 62–64°. There is three shorter (1.68 Å) and one longer (1.69 Å) Se–O bond length. In the second Se6+ site, Se6+ is bonded to four O2- atoms to form SeO4 tetrahedra that share corners with four NaO6 octahedra. The corner-sharing octahedra tilt angles range from 67–68°. All Se–O bond lengths are 1.68 Å. In the third Se6+ site, Se6+ is bonded to four O2- atoms to form SeO4 tetrahedra that share corners with four NaO6 octahedra and corners with four equivalent NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 62–64°. There is one shorter (1.67 Å) and three longer (1.68 Å) Se–O bond length. In the fourth Se6+ site, Se6+ is bonded to six O2- atoms to form SeO6 octahedra that share faces with four NaO6 octahedra and faces with two equivalent NaO6 pentagonal pyramids. There are a spread of Se–O bond distances ranging from 1.84–1.88 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+ and one Se6+ atom. In the second O2- site, O2- is bonded to five Na1+ and one Se6+ atom to form a mixture of distorted face and corner-sharing ONa5Se octahedra. The corner-sharing octahedral tilt angles are 0°. In the third O2- site, O2- is bonded to five Na1+ and one Se6+ atom to form a mixture of face and corner-sharing ONa5Se octahedra. The corner-sharing octahedra tilt angles range from 1–8°. In the fourth O2- site, O2- is bonded to five Na1+ and one Se6+ atom to form a mixture of face and corner-sharing ONa5Se octahedra. The corner-sharing octahedral tilt angles are 0°. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one Se6+ atom. In the sixth O2- site, O2- is bonded in a 5-coordinate geometry to four Na1+ and one Se6+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one Se6+ atom. In the eighth O2- site, O2- is bonded in a 5-coordinate geometry to four Na1+ and one Se6+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one Se6+ atom. In the tenth O2- site, O2- is bonded in a 5-coordinate geometry to four Na1+ and one Se6+ atom. In the eleventh O2- site, O2- is bonded to five Na1+ and one Se6+ atom to form a mixture of face and corner-sharing ONa5Se octahedra. The corner-sharing octahedra tilt angles range from 1–8°. In the twelfth O2- site, O2- is bonded to five Na1+ and one Se6+ atom to form a mixture of face and corner-sharing ONa5Se octahedra. The corner-sharing octahedra tilt angles range from 1–13°. In the thirteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+ and one Se6+ atom. In the fourteenth O2- site, O2- is bonded in a 5-coordinate geometry to four Na1+ and one Se6+ atom.