DOI: 10.17188/1288155
title: Materials Data on K2NaNb2Fe7Si8H4O31 by Materials Project

description: K2NaNb2Fe7Si8H4O31 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.79–2.86 Å. Na1+ is bonded in a distorted q6 geometry to ten O2- atoms. There are a spread of Na–O bond distances ranging from 2.66–2.75 Å. Nb2+ is bonded to six O2- atoms to form NbO6 octahedra that share a cornercorner with one NbO6 octahedra, corners with three FeO6 octahedra, and corners with four SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 0–60°. There are a spread of Nb–O bond distances ranging from 1.96–2.09 Å. There are four inequivalent Fe+2.71+ sites. In the first Fe+2.71+ site, Fe+2.71+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four SiO4 tetrahedra and edges with six FeO6 octahedra. There are two shorter (2.12 Å) and four longer (2.18 Å) Fe–O bond lengths. In the second Fe+2.71+ site, Fe+2.71+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one NbO6 octahedra, corners with three SiO4 tetrahedra, and edges with six FeO6 octahedra. The corner-sharing octahedral tilt angles are 59°. There are a spread of Fe–O bond distances ranging from 2.13–2.24 Å. In the third Fe+2.71+ site, Fe+2.71+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one NbO6 octahedra, corners with four SiO4 tetrahedra, and edges with six FeO6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are a spread of Fe–O bond distances ranging from 2.09–2.28 Å. In the fourth Fe+2.71+ site, Fe+2.71+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one NbO6 octahedra, corners with three SiO4 tetrahedra, and edges with six FeO6 octahedra. The corner-sharing octahedral tilt angles are 59°. There are a spread of Fe–O bond distances ranging from 2.11–2.27 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 corners with three FeO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–61°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is two shorter (1.63 Å) and two longer (1.66 Å) Si–O bond length. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent NbO6 octahedra, corners with three FeO6 octahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–63°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent NbO6 octahedra, corners with three FeO6 octahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 36–62°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to one Nb2+ and three Fe+2.71+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Fe+2.71+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to three Fe+2.71+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three Fe+2.71+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Fe+2.71+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to three Fe+2.71+ and one H1+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three Fe+2.71+ and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Na1+, one Nb2+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Na1+, one Nb2+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourteenth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Na1+, one Nb2+, and one Si4+ atom. In the fifteenth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Na1+, one Nb2+, and one Si4+ atom. In the sixteenth O2- site, O2- is bonded in a distorted linear geometry to two equivalent Na1+ and two equivalent Nb2+ atoms.