SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
LiFeSi2O6 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Li1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Li–O bond distances ranging from 2.07–2.42 Å. Fe3+ 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 1.94–2.18 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent FeO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 32–59°. There is one shorter (1.61 Å) and three longer (1.65 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent FeO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 40–60°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Fe3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Li1+, one Fe3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+ and two equivalent Si4+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Fe3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Fe3+, and one Si4+ atom.
LiFeSi2O6 is Esseneite structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.07–2.55 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six equivalent SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.94–2.18 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent 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 1.62–1.66 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Fe3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Fe3+, and one Si4+ atom.
MgFe(SiO3)2 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Mg2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Mg–O bond distances ranging from 2.07–2.29 Å. Fe2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are two shorter (2.13 Å) and six longer (2.31 Å) Fe–O bond lengths. Si4+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing SiO6 octahedra. The corner-sharing octahedra tilt angles range from 39–43°. There are a spread of Si–O bond distances ranging from 1.79–1.84 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to one Mg2+, two equivalent Fe2+, and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Mg2+, one Fe2+, and two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Fe2+ and two equivalent Si4+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Si4+ atoms to form distorted corner-sharing OMg2Si2 tetrahedra.
MgFe(SiO3)2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Mg2+ is bonded to six O2- atoms to form distorted MgO6 octahedra that share corners with six SiO4 tetrahedra, edges with three equivalent FeO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Mg–O bond distances ranging from 1.99–2.70 Å. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra, edges with two equivalent FeO6 octahedra, and edges with three equivalent MgO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.07–2.28 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent FeO6 octahedra, corners with four equivalent MgO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–75°. 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 corners with two equivalent MgO6 octahedra, corners with three equivalent FeO6 octahedra, corners with two equivalent SiO4 tetrahedra, and an edgeedge with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 27–60°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+, two equivalent Fe2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Fe2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Mg2+, one Fe2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent Si4+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mg2+ and two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+, two equivalent Fe2+, and one Si4+ atom.
Li2Fe(SiO3)2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four O2- atoms to form LiO4 tetrahedra that share corners with four equivalent LiO4 tetrahedra and corners with five SiO4 tetrahedra. There are a spread of Li–O bond distances ranging from 1.93–2.19 Å. In the second Li1+ site, Li1+ is bonded to four O2- atoms to form distorted LiO4 tetrahedra that share corners with five SiO4 tetrahedra and corners with six LiO4 tetrahedra. There are a spread of Li–O bond distances ranging from 2.01–2.19 Å. Fe2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Fe–O bond distances ranging from 1.93–2.10 Å. There are two 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 SiO4 tetrahedra and corners with three LiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.71 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent SiO4 tetrahedra and corners with seven LiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Fe2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Li1+, one Fe2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded to two Li1+ and two Si4+ atoms to form corner-sharing OLi2Si2 tetrahedra. In the fifth O2- site, O2- is bonded to two Li1+, one Fe2+, and one Si4+ atom to form distorted corner-sharing OLi2FeSi tetrahedra. In the sixth O2- site, O2- is bonded to three Li1+ and one Si4+ atom to form distorted corner-sharing OLi3Si tetrahedra.
Na3Li2Fe5(SiO3)10 is Esseneite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 8-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.42 Å. In the second Na1+ site, Na1+ is bonded in a 8-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.42 Å. In the third Na1+ site, Na1+ is bonded in a 8-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.42 Å. In the fourth Na1+ site, Na1+ is bonded in a 8-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.42 Å. In the fifth 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 2.37–2.98 Å. In the sixth Na1+ site, Na1+ is bonded in a 8-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.43 Å. There are four inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.18–2.53 Å. In the second Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.18–2.53 Å. In the third Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.18–2.53 Å. In the fourth Li1+ site, Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.18–2.54 Å. There are ten 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 and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.16 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.94–2.18 Å. In the third Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.16 Å. In the fourth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.94–2.18 Å. In the fifth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.16 Å. In the sixth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.94–2.18 Å. In the seventh Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.16 Å. In the eighth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.18 Å. In the ninth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.15 Å. In the tenth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.16 Å. There are twenty 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 SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–60°. There are a spread of Si–O bond distances ranging from 1.62–1.66 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 SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 36–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the third 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 35–58°. 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 three FeO6 octahedra and corners with two 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 fifth 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 36–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 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 36–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the seventh 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 33–60°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the eighth 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 33–60°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the ninth 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 36–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the tenth 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 36–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the eleventh 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 33–60°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the twelfth 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 34–59°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the thirteenth 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 36–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the fourteenth 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the fifteenth 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 33–60°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the sixteenth 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 33–60°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. In the seventeenth 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the eighteenth 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 34–58°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the nineteenth 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 34–58°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. In the twentieth 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 35–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. There are fifty-nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two Fe3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Fe3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Fe3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two Fe3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Fe3+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Fe3+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+ and two Si4+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Fe3+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two Fe3+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Fe3+, and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Na1+, one Fe3+, and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+ and two Si4+ atoms. In the fifteenth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Fe3+, and one Si4+ atom. In the sixteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Fe3+, and one Si4+ atom. In the seventeenth O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+ and two Si4+ atoms. In the eighteenth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, two Fe3+, and one Si4+ atom. In the nineteenth O2- site, O2- is bonded in a 2-coor
Ambient pressure Moessbauer spectra of Mg(0.9)Fe-57(0.1)SiO3 perovskite synthesized at pressure-temperature conditions of about 50 GPa and 1700 K show that the iron is entirely high-spin Fe(2+) and appears to be primarily located in the octahedral site within the crystal structure. We observe broad Moessbauer lines, suggesting a distribution of electric-field gradients caused by disorder associated with the Fe ions. Also, the perovskite exhibits magnetic ordering at temperatures lower than 5 K, implying that there is a magnetic contribution to the absolute ('third-law') entropy of this phase.
Na9LiFe10(SiO3)20 is Esseneite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are nine inequivalent Na sites. In the first Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.41–2.91 Å. In the second Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.91 Å. In the third Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.91 Å. In the fourth Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.93 Å. In the fifth Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.91 Å. In the sixth Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.92 Å. In the seventh Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.93 Å. In the eighth Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.91 Å. In the ninth Na site, Na is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Na–O bond distances ranging from 2.40–2.92 Å. Li is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Li–O bond distances ranging from 2.28–2.50 Å. There are ten inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.15 Å. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.15 Å. In the third Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.15 Å. In the fourth Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.16 Å. In the fifth Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.15 Å. In the sixth Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.15 Å. In the seventh Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.15 Å. In the eighth Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.15 Å. In the ninth Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.15 Å. In the tenth Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.15 Å. There are seventeen inequivalent Si sites. In the first Si site, Si is bonded to four O 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 34–60°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the second Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the third Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the fourth Si site, Si is bonded to four O 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 35–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the fifth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the sixth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the seventh Si site, Si is bonded to four O 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 35–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the eighth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the ninth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the tenth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the eleventh Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the twelfth Si site, Si is bonded to four O 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 35–58°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the thirteenth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the fourteenth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the fifteenth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the sixteenth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the seventeenth Si site, Si is bonded to four O 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 34–59°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. There are forty-eight inequivalent O sites. In the first O site, O is bonded in a distorted T-shaped geometry to one Na, one Fe, and one Si atom. In the second O site, O is bonded in a 2-coordinate geometry to two Na and two Si atoms. In the third O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the fourth O site, O is bonded in a distorted T-shaped geometry to one Na, one Fe, and one Si atom. In the fifth O site, O is bonded in a distorted T-shaped geometry to one Na, one Fe, and one Si atom. In the sixth O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the seventh O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the eighth O site, O is bonded in a 2-coordinate geometry to two Na and two Si atoms. In the ninth O site, O is bonded in a distorted T-shaped geometry to one Na, one Fe, and one Si atom. In the tenth O site, O is bonded to one Li, two Fe, and one Si atom to form distorted edge-sharing OLiFe2Si tetrahedra. In the eleventh O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the twelfth O site, O is bonded in a 2-coordinate geometry to two Na and two Si atoms. In the thirteenth O site, O is bonded in a distorted T-shaped geometry to one Li, one Fe, and one Si atom. In the fourteenth O site, O is bonded in a 2-coordinate geometry to two Na and two Si atoms. In the fifteenth O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the sixteenth O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the seventeenth O site, O is bonded in a 3-coordinate geometry to one Na and two Si atoms. In the eighteenth O site, O is bonded in a distorted T-shaped geometry to one Na, one Fe, and one Si atom. In the nineteenth O site, O is bonded in a distorted T-shaped geometry to one Na, one Fe, and one Si atom. In the twentieth O site, O is bonded in a 2-coordinate geometry to two Na and two Si atoms. In the twenty-first O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the twenty-second O site, O is bonded in a 2-coordinate geometry to one Na, one Li, and two Si atoms. In the twenty-third O site, O is bonded in a distorted T-shaped geometry to one Na, one Fe, and one Si atom. In the twenty-fourth O site, O is bonded in a 2-coordinate geometry to two Na and two Si atoms. In the twenty-fifth O site, O is bonded to one Li, two Fe, and one Si atom to form distorted edge-sharing OLiFe2Si tetrahedra. The O–Si bond length is 1.65 Å. In the twenty-sixth O site, O is bonded in a 2-coordinate geometry to two Na and two Si atoms. In the twenty-seventh O site, O is bonded in a distorted T-shaped geometry to one Na, one Fe, and one Si atom. In the twenty-eighth O site, O is bonded in a 2-coordinate geometry to two Na and two Si atoms. In the twenty-ninth O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the thirtieth O site, O is bonded in a 4-coordinate geometry to one Na, two Fe, and one Si atom. In the thirty-first O site, O is bonded in a 2-coordinate geometry to two Na
Ca2MgFe(SiO3)4 is Esseneite-derived structured and crystallizes in the monoclinic C2 space group. The structure is three-dimensional. 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 2.34–2.81 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 2.35–2.80 Å. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.15 Å. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.11–2.20 Å. There are two 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 equivalent MgO6 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 1.60–1.71 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with two equivalent FeO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–60°. There are a spread of Si–O bond distances ranging from 1.61–1.70 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Mg2+, 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 4-coordinate geometry to one Ca2+, one Mg2+, one Fe2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Mg2+, one Fe2+, 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 two Ca2+ and two Si4+ atoms.
Ca2FeZn(SiO3)4 is Esseneite-derived structured and crystallizes in the monoclinic C2 space group. The structure is three-dimensional. 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 2.35–2.78 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 2.35–2.78 Å. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent ZnO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.12–2.20 Å. Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.11–2.20 Å. There are two 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 equivalent ZnO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–58°. There are a spread of Si–O bond distances ranging from 1.61–1.70 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one ZnO6 octahedra, corners with two equivalent FeO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–58°. There are a spread of Si–O bond distances ranging from 1.60–1.71 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Zn2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Zn2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Zn2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Fe2+, 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 two Ca2+ and two Si4+ atoms.
Ca4FeZn3(SiO3)8 is Esseneite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four 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 2.35–2.79 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 2.35–2.79 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. In the fourth 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. Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent ZnO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.11–2.20 Å. There are three inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent ZnO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.10–2.20 Å. In the second Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent ZnO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.10–2.20 Å. In the third Zn2+ site, Zn2+ is bonded to six O2- atoms to form ZnO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Zn–O bond distances ranging from 2.10–2.20 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 ZnO6 octahedra, corners with two equivalent FeO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–59°. There are a spread of Si–O bond distances ranging from 1.60–1.71 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three ZnO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–58°. There are a spread of Si–O bond distances ranging from 1.61–1.71 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one FeO6 octahedra, corners with two ZnO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–58°. 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 FeO6 octahedra, corners with two ZnO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–58°. There are a spread of Si–O bond distances ranging from 1.61–1.71 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three ZnO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–58°. There are a spread of Si–O bond distances ranging from 1.61–1.71 Å. In the sixth 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 ZnO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–58°. There are a spread of Si–O bond distances ranging from 1.61–1.71 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 ZnO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–59°. There are a spread of Si–O bond distances ranging from 1.61–1.70 Å. In the eighth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three ZnO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–58°. There are a spread of Si–O bond distances ranging from 1.61–1.71 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Zn2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Zn2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Zn2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Zn2+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Zn2+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Zn2+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Fe2+, one Zn2+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Zn2+, 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 distorted T-shaped geometry to one Ca2+, one Zn2+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Zn2+, and one Si4+ atom. In the thirteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Zn2+, and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Zn2+, and one Si4+ atom. In the fifteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Zn2+, and one Si4+ atom. In the sixteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Zn2+, and one Si4+ atom. In the seventeenth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the eighteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the nineteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the twentieth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the twenty-first O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the twenty-second O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the twenty-third O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the twenty-fourth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms.