Materials Data on K2Nb2As2O11 by Materials Project
K2Nb2As2O11 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are four inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.90–3.20 Å. In the second K1+ site, K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.92–3.22 Å. In the third K1+ site, K1+ is bonded to eight O2- atoms to form distorted KO8 hexagonal bipyramids that share corners with two NbO6 octahedra, corners with two AsO4 tetrahedra, and edges with four NbO6 octahedra. The corner-sharing octahedral tilt angles are 61°. There are a spread of K–O bond distances ranging from 2.88–3.03 Å. In the fourth K1+ site, K1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of K–O bond distances ranging from 2.74–3.21 Å. There are four inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share a cornercorner with one NbO6 octahedra, corners with four AsO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 27°. There are a spread of Nb–O bond distances ranging from 1.77–2.31 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share a cornercorner with one NbO6 octahedra, corners with four AsO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 26°. There are a spread of Nb–O bond distances ranging from 1.77–2.34 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share a cornercorner with one KO8 hexagonal bipyramid, a cornercorner with one NbO6 octahedra, corners with four AsO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 27°. There are a spread of Nb–O bond distances ranging from 1.79–2.26 Å. In the fourth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share a cornercorner with one KO8 hexagonal bipyramid, a cornercorner with one NbO6 octahedra, corners with four AsO4 tetrahedra, and an edgeedge with one KO8 hexagonal bipyramid. The corner-sharing octahedral tilt angles are 26°. There are a spread of Nb–O bond distances ranging from 1.79–2.26 Å. There are four inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with four NbO6 octahedra. The corner-sharing octahedra tilt angles range from 46–54°. There are a spread of As–O bond distances ranging from 1.70–1.76 Å. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with four NbO6 octahedra. The corner-sharing octahedra tilt angles range from 46–54°. There are a spread of As–O bond distances ranging from 1.69–1.76 Å. In the third As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one KO8 hexagonal bipyramid and corners with four NbO6 octahedra. The corner-sharing octahedra tilt angles range from 52–56°. All As–O bond lengths are 1.72 Å. In the fourth As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one KO8 hexagonal bipyramid and corners with four NbO6 octahedra. The corner-sharing octahedra tilt angles range from 52–56°. All As–O bond lengths are 1.72 Å. There are twenty-two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Nb5+ atoms. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one K1+ and two Nb5+ atoms. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one Nb5+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two K1+ and one Nb5+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Nb5+, and one As5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Nb5+ and one As5+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Nb5+, and one As5+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Nb5+, and one As5+ atom. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to one Nb5+ and one As5+ atom. In the tenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Nb5+ and one As5+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one Nb5+ atom. In the twelfth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+ and one Nb5+ atom. In the thirteenth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Nb5+, and one As5+ atom. In the fourteenth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Nb5+, and one As5+ atom. In the fifteenth O2- site, O2- is bonded in a 1-coordinate geometry to one K1+, one Nb5+, and one As5+ atom. In the sixteenth O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Nb5+, and one As5+ atom. In the seventeenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+, one Nb5+, and one As5+ atom. In the eighteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+, one Nb5+, and one As5+ atom. In the nineteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two K1+, one Nb5+, and one As5+ atom. In the twentieth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two K1+, one Nb5+, and one As5+ atom. In the twenty-first O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Nb5+, and one As5+ atom. In the twenty-second O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, one Nb5+, and one As5+ atom.