Materials Data on KNbSi2O7 by Materials Project
KNbSi2O7 crystallizes in the tetragonal P4bm space group. The structure is three-dimensional. K1+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of K–O bond distances ranging from 2.90–3.27 Å. There are two inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent NbO6 octahedra and corners with four equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Nb–O bond distances ranging from 1.80–2.30 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with two equivalent NbO6 octahedra and corners with four equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Nb–O bond distances ranging from 1.81–2.36 Å. There are two inequivalent Si4+ sites. In the first 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 octahedral tilt angles are 31°. There is three shorter (1.62 Å) and one longer (1.66 Å) Si–O bond length. 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 octahedral tilt angles are 18°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to two Nb5+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to four equivalent K1+ and two Nb5+ atoms. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+, one Nb5+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+, one Nb5+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+ and two equivalent Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+ and two equivalent Si4+ atoms.