Materials Data on KCa2(SiO3)8 by Materials Project
KCa2(SiO3)8 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. K is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of K–O bond distances ranging from 2.85–2.89 Å. There are two inequivalent Ca sites. In the first Ca site, Ca is bonded to six O atoms to form distorted CaO6 octahedra that share corners with four SiO4 tetrahedra and edges with two equivalent CaO6 octahedra. There are four shorter (2.27 Å) and two longer (2.93 Å) Ca–O bond lengths. In the second Ca site, Ca is bonded to six O atoms to form CaO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent CaO6 octahedra. There are four shorter (2.38 Å) and two longer (2.40 Å) Ca–O bond lengths. 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 1.61–1.64 Å. In the second 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 47–55°. There are a spread of Si–O bond distances ranging from 1.60–1.67 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 46–55°. There are a spread of Si–O bond distances ranging from 1.60–1.67 Å. 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 49°. There is two shorter (1.63 Å) and two longer (1.64 Å) Si–O bond length. There are thirteen inequivalent O sites. In the first O site, O is bonded in a water-like geometry to one K and one O atom. The O–O bond length is 1.29 Å. In the second O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent O atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the fourth O site, O is bonded in a bent 120 degrees geometry to one Ca and one O atom. The O–O bond length is 1.23 Å. In the fifth O site, O is bonded in a distorted trigonal planar geometry to two Ca and one Si atom. In the sixth O site, O is bonded in a distorted trigonal planar geometry to two Ca and one Si atom. In the seventh O site, O is bonded in a distorted bent 150 degrees geometry to one K and two Si atoms. In the eighth O site, O is bonded in a 2-coordinate geometry to one K and two Si atoms. In the ninth O site, O is bonded in a 2-coordinate geometry to one K and two Si atoms. In the tenth O site, O is bonded in a linear geometry to two Si atoms. In the eleventh O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the twelfth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the thirteenth O site, O is bonded in a distorted bent 120 degrees geometry to one Ca and one Si atom.