Materials Data on NaCaNb2O6F by Materials Project

Abstract

NaCaNb2O6F crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Na1+ is bonded to six O2- and two equivalent F1- atoms to form distorted NaO6F2 hexagonal bipyramids that share edges with two equivalent NaO6F2 hexagonal bipyramids, edges with four equivalent CaO6F2 hexagonal bipyramids, and edges with six NbO6 octahedra. There are two shorter (2.71 Å) and four longer (2.72 Å) Na–O bond lengths. Both Na–F bond lengths are 2.32 Å. Ca2+ is bonded to six O2- and two equivalent F1- atoms to form distorted CaO6F2 hexagonal bipyramids that share edges with two equivalent CaO6F2 hexagonal bipyramids, edges with four equivalent NaO6F2 hexagonal bipyramids, and edges with six NbO6 octahedra. There are four shorter (2.64 Å) and two longer (2.66 Å) Ca–O bond lengths. Both Ca–F bond lengths are 2.26 Å. There are two inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra, edges with two equivalent CaO6F2 hexagonal bipyramids, and edges with four equivalent NaO6F2 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 39–42°. There are two shorter (2.00 Å) and four longer (2.01 Å) Nb–O bond lengths. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra, edges with two equivalent NaO6F2 hexagonal bipyramids, and edges with four equivalent CaO6F2 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 42–45°. There are four shorter (2.00 Å) and two longer (2.01 Å) Nb–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Ca2+, and two Nb5+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Na1+ and two equivalent Nb5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Nb5+ atoms. F1- is bonded to two equivalent Na1+ and two equivalent Ca2+ atoms to form corner-sharing FNa2Ca2 tetrahedra.