Materials Data on K2Ca2Si8O23 by Materials Project
K2Ca2Si8O23 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. K is bonded in a 6-coordinate geometry to six O atoms. There are a spread of K–O bond distances ranging from 2.75–3.28 Å. Ca is bonded to six O atoms to form distorted CaO6 octahedra that share corners with five SiO4 tetrahedra and edges with two equivalent CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.32–2.63 Å. There are four inequivalent Si sites. In the first 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 1.61–1.63 Å. In the second 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 55–58°. There are a spread of Si–O bond distances ranging from 1.60–1.65 Å. In the third 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 44°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the fourth 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 50–54°. There are a spread of Si–O bond distances ranging from 1.60–1.66 Å. There are twelve inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the second O site, O is bonded in a distorted bent 150 degrees geometry to one Ca and one Si atom. In the third O site, O is bonded in a distorted trigonal planar geometry to two equivalent Ca and one Si atom. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one K and two Si atoms. In the fifth O site, O is bonded in a distorted bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to one K and one O atom. The O–O bond length is 1.23 Å. In the seventh O site, O is bonded in an L-shaped geometry to one K and one Ca atom. In the eighth O site, O is bonded in a linear geometry to two equivalent 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 in a distorted bent 150 degrees geometry to one K and two Si atoms. In the eleventh O site, O is bonded in a 1-coordinate geometry to one K, two equivalent Ca, and one Si atom. In the twelfth O site, O is bonded in a distorted bent 150 degrees geometry to one K and two Si atoms.