DOE OSTI2020
K2Ca3Si3O10 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.66–3.32 Å. In the second K1+ site, K1+ is bonded to eight O2- atoms to form distorted KO8 hexagonal bipyramids that share corners with two equivalent KO8 hexagonal bipyramids, corners with four CaO6 octahedra, corners with two SiO4 tetrahedra, edges with two equivalent CaO6 octahedra, edges with three SiO4 tetrahedra, a faceface with one CaO6 octahedra, and a faceface with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 12–50°. There are a spread of K–O bond distances ranging from 2.69–2.98 Å. There are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with two equivalent CaO6 octahedra, corners with six SiO4 tetrahedra, a faceface with one KO8 hexagonal bipyramid, and faces with two CaO6 octahedra. The corner-sharing octahedra tilt angles range from 71–86°. There are a spread of Ca–O bond distances ranging from 2.29–2.57 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share a cornercorner with one KO8 hexagonal bipyramid, corners with six SiO4 tetrahedra, edges with two equivalent KO8 hexagonal bipyramids, edges with three CaO6 octahedra, and a faceface with one CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.36–2.49 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with three equivalent KO8 hexagonal bipyramids, corners with two equivalent CaO6 octahedra, corners with four SiO4 tetrahedra, edges with two equivalent CaO6 octahedra, an edgeedge with one SiO4 tetrahedra, and a faceface with one CaO6 octahedra. The corner-sharing octahedra tilt angles range from 71–86°. There are a spread of Ca–O bond distances ranging from 2.33–2.63 Å. There are three 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 KO8 hexagonal bipyramid and corners with eight CaO6 octahedra. The corner-sharing octahedra tilt angles range from 19–65°. There are a spread of Si–O bond distances ranging from 1.65–1.67 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one KO8 hexagonal bipyramid, corners with four CaO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with two equivalent KO8 hexagonal bipyramids, and an edgeedge with one CaO6 octahedra. The corner-sharing octahedra tilt angles range from 20–68°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four CaO6 octahedra, corners with two equivalent SiO4 tetrahedra, an edgeedge with one KO8 hexagonal bipyramid, and a faceface with one KO8 hexagonal bipyramid. The corner-sharing octahedra tilt angles range from 50–65°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, two Ca2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one K1+, two equivalent Ca2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 6-coordinate geometry to four K1+, one Ca2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to one K1+, two Ca2+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent K1+, two Ca2+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, three Ca2+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, three Ca2+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the tenth O2- site, O2- is bonded in a 2-coordinate geometry to three K1+ and two Si4+ atoms.