DOE OSTI2020
NaCaFeAl(SiO3)4 is Esseneite-derived structured and crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are two 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 2.31–2.92 Å. In the second 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 2.37–2.88 Å. There are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.30–2.82 Å. In the second Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.32–2.75 Å. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra, an edgeedge with one FeO6 octahedra, and an edgeedge with one AlO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.08–2.20 Å. In the second Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.10–2.14 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six SiO4 tetrahedra, an edgeedge with one FeO6 octahedra, and an edgeedge with one AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–2.07 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.13 Å. There are six inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three AlO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 30–59°. There are a spread of Si–O bond distances ranging from 1.63–1.68 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 AlO6 octahedra, and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 32–65°. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three AlO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 39–60°. There are a spread of Si–O bond distances ranging from 1.59–1.70 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two equivalent FeO6 octahedra, and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 36–65°. There are a spread of Si–O bond distances ranging from 1.59–1.70 Å. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 37–61°. There are a spread of Si–O bond distances ranging from 1.60–1.70 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ca2+, and two Si4+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Al3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Fe2+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+ and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Al3+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Al3+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ca2+, and two Si4+ atoms. In the eleventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Fe2+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Fe2+, and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Al3+, and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the fifteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the sixteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the seventeenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the eighteenth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Fe2+, and one Si4+ atom.