Materials Data on K2Ca4Si8O21 by Materials Project
K2Ca4Si8O21 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. K1+ is bonded in a 1-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.65–3.41 Å. There are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.27–2.64 Å. In the second Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.35–2.95 Å. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.59–1.66 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.67 Å. There are eleven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent K1+ and two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ca2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to three Ca2+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+ and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Ca2+, and two Si4+ atoms. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent K1+, one Ca2+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, two Ca2+, and one Si4+ atom.