Materials Data on Ca7(Si2O5)8 by Materials Project
Ca7(Si2O5)8 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Ca sites. In the first Ca site, Ca is bonded to six O atoms to form distorted CaO6 octahedra that share corners with five SiO4 tetrahedra and edges with three CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.32–2.50 Å. In the second Ca site, Ca is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Ca–O bond distances ranging from 2.30–2.51 Å. In the third Ca site, Ca is bonded to six O atoms to form CaO6 octahedra that share corners with six SiO4 tetrahedra and edges with three CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.37–2.49 Å. In the fourth Ca site, Ca is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.31–2.92 Å. There are eight inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two equivalent CaO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–60°. There is two shorter (1.63 Å) and two longer (1.64 Å) Si–O bond length. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 60°. All Si–O bond lengths are 1.63 Å. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two CaO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–72°. There is one shorter (1.62 Å) and three longer (1.63 Å) Si–O bond length. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. All Si–O bond lengths are 1.63 Å. In the fifth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two CaO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–59°. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. In the sixth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three CaO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–73°. There is one shorter (1.62 Å) and three longer (1.63 Å) Si–O bond length. In the seventh Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There is one shorter (1.61 Å) and three longer (1.63 Å) Si–O bond length. In the eighth Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.64 Å. There are twenty inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to two Si atoms. In the second O site, O is bonded in a distorted linear geometry to one Ca and two Si atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the seventh O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the eighth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the ninth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the tenth O site, O is bonded to three Ca and one Si atom to form a mixture of distorted corner and edge-sharing OCa3Si trigonal pyramids. In the eleventh O site, O is bonded to three Ca and one Si atom to form a mixture of distorted corner and edge-sharing OCa3Si trigonal pyramids. In the twelfth O site, O is bonded to three Ca and one Si atom to form a mixture of distorted corner and edge-sharing OCa3Si tetrahedra. In the thirteenth O site, O is bonded to three Ca and one Si atom to form a mixture of distorted corner and edge-sharing OCa3Si trigonal pyramids. In the fourteenth O site, O is bonded to three Ca and one Si atom to form a mixture of distorted corner and edge-sharing OCa3Si trigonal pyramids. In the fifteenth O site, O is bonded to three Ca and one Si atom to form a mixture of distorted corner and edge-sharing OCa3Si tetrahedra. In the sixteenth O site, O is bonded in a bent 120 degrees geometry to two Si atoms. In the seventeenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the eighteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the nineteenth O site, O is bonded in a linear geometry to two Si atoms. In the twentieth O site, O is bonded in a trigonal non-coplanar geometry to three Ca atoms.