DOE OSTI2020
Na12Ca3Fe2(Si6O18)2 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. there are eight inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.24–2.91 Å. In the second Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with three NaO8 hexagonal bipyramids, a cornercorner with one SiO4 tetrahedra, edges with two equivalent NaO8 hexagonal bipyramids, an edgeedge with one CaO6 octahedra, an edgeedge with one FeO6 octahedra, an edgeedge with one NaO6 pentagonal pyramid, edges with five SiO4 tetrahedra, and a faceface with one CaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.29–2.84 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 2.33–2.66 Å. In the fourth Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with two equivalent NaO8 hexagonal bipyramids, a cornercorner with one SiO4 tetrahedra, edges with three NaO8 hexagonal bipyramids, an edgeedge with one CaO6 octahedra, an edgeedge with one FeO6 octahedra, edges with five SiO4 tetrahedra, and a faceface with one CaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.36–2.78 Å. In the fifth Na1+ site, Na1+ is bonded in a 3-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.24–2.97 Å. In the sixth Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.67–2.74 Å. In the seventh Na1+ site, Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share corners with two equivalent NaO8 hexagonal bipyramids, corners with two SiO4 tetrahedra, edges with two equivalent NaO8 hexagonal bipyramids, edges with two equivalent FeO6 octahedra, edges with four SiO4 tetrahedra, and faces with two CaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.27–2.83 Å. In the eighth Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share a cornercorner with one CaO6 octahedra, corners with four SiO4 tetrahedra, edges with two equivalent NaO8 hexagonal bipyramids, an edgeedge with one FeO6 octahedra, and edges with two equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 84°. There are a spread of Na–O bond distances ranging from 2.28–2.49 Å. There are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share a cornercorner with one NaO6 pentagonal pyramid, corners with six SiO4 tetrahedra, edges with two equivalent NaO8 hexagonal bipyramids, faces with two equivalent NaO8 hexagonal bipyramids, and a faceface with one FeO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.29–2.48 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with six SiO4 tetrahedra, a faceface with one NaO8 hexagonal bipyramid, and a faceface with one FeO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.29–2.48 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with six SiO4 tetrahedra, edges with two equivalent NaO8 hexagonal bipyramids, faces with three NaO8 hexagonal bipyramids, and a faceface with one FeO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.23–2.47 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra, edges with four NaO8 hexagonal bipyramids, and faces with two CaO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.06–2.11 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra, edges with two equivalent NaO8 hexagonal bipyramids, an edgeedge with one NaO6 pentagonal pyramid, and a faceface with one CaO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.01–2.16 Å. There are eight inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one FeO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 35°. There are a spread of Si–O bond distances ranging from 1.59–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one FeO6 octahedra, corners with two equivalent CaO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, corners with two equivalent SiO4 tetrahedra, and edges with four NaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 38–47°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO8 hexagonal bipyramid, a cornercorner with one FeO6 octahedra, corners with two equivalent CaO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–46°. There are a spread of Si–O bond distances ranging from 1.60–1.68 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO8 hexagonal bipyramid, a cornercorner with one FeO6 octahedra, corners with two equivalent CaO6 octahedra, corners with two equivalent SiO4 tetrahedra, and edges with four NaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 33–45°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra, a cornercorner with one FeO6 octahedra, corners with two SiO4 tetrahedra, and edges with three NaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 41–51°. There are a spread of Si–O bond distances ranging from 1.58–1.68 Å. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO8 hexagonal bipyramid, a cornercorner with one FeO6 octahedra, corners with two CaO6 octahedra, corners with two SiO4 tetrahedra, and edges with two NaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 33–51°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the seventh Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one FeO6 octahedra, corners with two CaO6 octahedra, a cornercorner with one NaO6 pentagonal pyramid, corners with two SiO4 tetrahedra, and edges with two NaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 34–51°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. In the eighth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NaO8 hexagonal bipyramid, a cornercorner with one CaO6 octahedra, a cornercorner with one FeO6 octahedra, corners with two SiO4 tetrahedra, an edgeedge with one NaO8 hexagonal bipyramid, and an edgeedge with one NaO6 pentagonal pyramid. The corner-sharing octahedra tilt angles range from 28–30°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. There are twenty-two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Fe3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Ca2+, one Fe3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+, one Ca2+, one Fe3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two Na1+, one Ca2+, one Fe3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded to three Na1+ and one Si4+ atom to form distorted corner-sharing ONa3Si tetrahedra. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Ca2+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+, one Ca2+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+, one Ca2+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+ and two Si4+ atoms. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to three Na1+ and two Si4+ atoms. In the eleventh O2- site, O2- is bonded in a 5-coordinate geometry to four Na1+ and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+, one Ca2+, and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Ca2+, and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Na1+, one Ca2+, and one Si4+ atom. In the fifteenth O2- site, O2- is bonded in a 2-coordinate geometry to three Na1+ and two Si4+ atoms. In the sixteenth O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+ and two Si4+ atoms. In the seventeenth O2- site, O2- is bonded in a 2-coordinate geometry to three Na1+ and two Si4+ atoms. In the eighteenth O2- site, O2- is bonded in a 2-coordinate geometry to three Na1+ and two Si4+ atoms. In the nineteenth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Na1+, one Ca2+, one Fe3+, and one Si4+ atom. In the twentieth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Na1+, one Ca2+, one Fe3+, and one Si4+ atom. In the twenty-first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+, one Fe3+, and one Si4+ atom. In the twenty-second O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Na1+, one Ca2+, one Fe3+, and one Si4+ atom.