Materials Data on KNaCa2(SiO3)8 by Materials Project
KNaCa2(SiO3)8 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. K is bonded to eight O atoms to form distorted KO8 hexagonal bipyramids that share corners with four SiO4 tetrahedra and edges with four SiO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.94–3.22 Å. Na is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Na–O bond distances ranging from 2.28–2.85 Å. There are two inequivalent Ca sites. In the first Ca site, Ca is bonded in a 5-coordinate geometry to six O atoms. There are a spread of Ca–O bond distances ranging from 2.21–3.05 Å. In the second Ca site, Ca is bonded to six O atoms to form CaO6 octahedra that share corners with five SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.26–2.44 Å. There are eight 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 1.60–1.65 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra, corners with three SiO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 58°. There are a spread of Si–O bond distances ranging from 1.61–1.66 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, corners with three SiO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 56°. 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 corners with two equivalent KO8 hexagonal bipyramids and corners with four SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.64 Å. In the fifth 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 41°. There are a spread of Si–O bond distances ranging from 1.60–1.65 Å. In the sixth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra, corners with three SiO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 48°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the seventh Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra, corners with three SiO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 45°. There are a spread of Si–O bond distances ranging from 1.60–1.67 Å. In the eighth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two equivalent KO8 hexagonal bipyramids and corners with four SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.63 Å. There are twenty-four inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to one K and two Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to 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 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 one K and two Si atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to one K and two Si atoms. In the seventh O site, O is bonded in a 3-coordinate geometry to two Ca and one Si atom. In the eighth O site, O is bonded in a distorted trigonal planar geometry to two Ca and one Si atom. In the ninth O site, O is bonded in a linear geometry to two Si atoms. In the tenth O site, O is bonded in a bent 120 degrees geometry to one Na and one Ca atom. 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 distorted trigonal non-coplanar geometry to one Na, one Ca, and one Si atom. In the thirteenth O site, O is bonded in a bent 120 degrees geometry to one K and one O atom. The O–O bond length is 1.23 Å. In the fourteenth O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.23 Å. In the fifteenth O site, O is bonded in a 3-coordinate geometry to one Na, one Ca, and one O atom. In the sixteenth O site, O is bonded in a distorted trigonal non-coplanar geometry to one Na, one Ca, and one Si atom. In the seventeenth O site, O is bonded in a distorted trigonal pyramidal geometry to one Na, two Ca, and one Si atom. In the eighteenth O site, O is bonded in a distorted trigonal planar geometry to two Ca and one Si atom. In the nineteenth O site, O is bonded in a distorted bent 150 degrees geometry to one K and two Si atoms. In the twentieth O site, O is bonded in a distorted bent 150 degrees geometry to one K and two Si atoms. In the twenty-first O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the twenty-second O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the twenty-third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the twenty-fourth O site, O is bonded in a bent 120 degrees geometry to one K and one O atom.