Materials Data on K4Nb2Si8O23 by Materials Project
K4Nb2Si8O23 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 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.76–3.00 Å. In the second K1+ site, K1+ is bonded in a 2-coordinate geometry to ten O2- atoms. There are a spread of K–O bond distances ranging from 2.79–3.50 Å. Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with five SiO4 tetrahedra. There are a spread of Nb–O bond distances ranging from 1.80–2.26 Å. There are four 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 NbO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. There are a spread of Si–O bond distances ranging from 1.60–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent NbO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 30–38°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NbO6 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 1.61–1.65 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 17°. There are a spread of Si–O bond distances ranging from 1.60–1.65 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Nb5+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent K1+ and two Si4+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two K1+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+, one Nb5+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one K1+, one Nb5+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Nb5+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one Nb5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent K1+ and two Si4+ atoms. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Nb5+, and one Si4+ atom.