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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NaCaMgAl(SiO3)4 by Materials Project

NaCaMgAl(SiO3)4 crystallizes in the monoclinic Pc space group. The structure is three-dimensional. Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.16–2.76 Å. Ca2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Ca–O bond distances ranging from 2.25–2.87 Å. Mg2+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are a spread of Mg–O bond distances ranging from 1.93–2.22 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with two equivalent SiO5 trigonal bipyramids. There are a spread of Al–O bond distances ranging from 1.76–1.80 Å. There are four 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 SiO4 tetrahedra and a cornercorner with one SiO5 trigonal bipyramid. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, and corners with two equivalent SiO5 trigonal bipyramids. There are a spread of Si–O bond distances ranging from 1.60–1.75 Å. In the third Si4+ site, Si4+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of Si–O bond distances ranging from 1.56–1.62 Å. In the fourth Si4+ site, Si4+ is bonded to five O2- atoms to form SiO5 trigonal bipyramids that share corners with two equivalent AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.69–1.79 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to one Na1+ and one Si4+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two equivalent Ca2+, and one Al3+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Mg2+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Al3+ and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a trigonal planar geometry to one Mg2+, one Al3+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 1-coordinate geometry to one Na1+, one Ca2+, one Mg2+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2CeAl(SiO3)4 by Materials Project

K2CeAl(SiO3)4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.84–3.29 Å. In the second K1+ site, K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.78–3.08 Å. Ce3+ is bonded to seven O2- atoms to form distorted CeO7 pentagonal bipyramids that share a cornercorner with one AlO4 tetrahedra, corners with five SiO4 tetrahedra, edges with two equivalent CeO7 pentagonal bipyramids, and an edgeedge with one SiO4 tetrahedra. There are a spread of Ce–O bond distances ranging from 2.35–2.82 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one CeO7 pentagonal bipyramid and corners with four SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.75–1.77 Å. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent CeO7 pentagonal bipyramids and corners with two SiO4 tetrahedra. There is two shorter (1.62 Å) and two longer (1.68 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CeO7 pentagonal bipyramid, a cornercorner with one AlO4 tetrahedra, corners with two SiO4 tetrahedra, and an edgeedge with one CeO7 pentagonal bipyramid. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent CeO7 pentagonal bipyramids, a cornercorner with one AlO4 tetrahedra, and corners with two SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent AlO4 tetrahedra and corners with two SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Ce3+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one K1+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ce3+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, two equivalent Ce3+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+ and two Si4+ atoms. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+, one Ce3+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Ce3+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+, one Al3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaCa3AlFe3(SiO3)8 by Materials Project

NaCa3Fe3Al(SiO3)8 is Esseneite-derived structured and crystallizes in the monoclinic P2 space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.39–2.79 Å. There are three 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 2.35–2.85 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 2.31–2.76 Å. In the third 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 2.35–2.79 Å. There are three 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 and edges with two equivalent FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.09–2.18 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 AlO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.08–2.18 Å. In the third 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 four shorter (2.14 Å) and two longer (2.22 Å) Fe–O bond lengths. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.04 Å. There are four 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 AlO6 octahedra, corners with two FeO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–62°. There are a spread of Si–O bond distances ranging from 1.60–1.70 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–59°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two FeO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–64°. There are a spread of Si–O bond distances ranging from 1.61–1.70 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two FeO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–59°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ca2+, and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Ca2+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ca2+, and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Fe2+, one Al3+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Fe2+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Al3+, 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.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na4Al3Fe(SiO3)8 by Materials Project

Na4FeAl3(SiO3)8 is Esseneite-derived structured and crystallizes in the monoclinic P2 space group. The structure is three-dimensional. there are four 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 2.38–2.80 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 2.40–2.82 Å. In the third 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 2.39–2.81 Å. In the fourth 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 2.40–2.80 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.12 Å. There are three 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 and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 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 FeO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.03 Å. In the third 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 1.88–2.04 Å. There are four 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, corners with two AlO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–60°. There are a spread of Si–O bond distances ranging from 1.61–1.66 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 AlO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–59°. There are a spread of Si–O bond distances ranging from 1.61–1.66 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 equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–60°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one FeO6 octahedra, corners with two AlO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 32–63°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Fe3+, 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 Fe3+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two Na1+ and two Si4+ atoms. 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 2-coordinate geometry to two Na1+ and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Fe3+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Al3+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Al3+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Al3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaCa3AlFe3(SiO3)8 by Materials Project

NaCa3Fe3Al(SiO3)8 is Esseneite-derived structured and crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.39–2.78 Å. There are three 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 2.36–2.87 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 2.33–2.82 Å. In the third 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 2.32–2.85 Å. There are three 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 and edges with two equivalent AlO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.11–2.19 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 2.10–2.18 Å. In the third 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 2.13–2.20 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.03 Å. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 32–60°. There are a spread of Si–O bond distances ranging from 1.60–1.70 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–60°. There are a spread of Si–O bond distances ranging from 1.60–1.70 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two FeO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–64°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. In the fourth 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 equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–61°. There are a spread of Si–O bond distances ranging from 1.61–1.68 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+, one Ca2+, and two Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Fe2+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+, one Ca2+, and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Fe2+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Al3+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Al3+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Fe2+, one Al3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCa3Mg3Al(SiO3)8 by Materials Project

KCa3Mg3Al(SiO3)8 is Esseneite-derived structured and crystallizes in the monoclinic P2 space group. The structure is three-dimensional. K1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.54–2.76 Å. There are three 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 2.37–2.77 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 2.39–2.72 Å. In the third 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 2.35–2.68 Å. There are three inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.13 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.17 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.19 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–2.06 Å. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–60°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–58°. There are a spread of Si–O bond distances ranging from 1.60–1.71 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 28–60°. There are a spread of Si–O bond distances ranging from 1.62–1.70 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–63°. There are a spread of Si–O bond distances ranging from 1.60–1.71 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Ca2+, and two Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Ca2+, and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Mg2+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one K1+, one Mg2+, one Al3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Mg2+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Mg2+, one Al3+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Mg2+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Mg2+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a distorted T-shaped geometry to one K1+, one Al3+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Mg2+, and one Si4+ atom.

36 MATERIALS SCIENCE↗