Materials Data on Na2NbAsO6 by Materials Project

Abstract

Na2NbAsO6 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 pentagonal pyramids that share a cornercorner with one NaO6 octahedra, corners with four equivalent AsO4 tetrahedra, an edgeedge with one NaO6 octahedra, edges with three equivalent NbO6 octahedra, and an edgeedge with one NaO6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 85°. There are a spread of Na–O bond distances ranging from 2.34–2.68 Å. In the second Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with two equivalent NbO6 octahedra, corners with two equivalent NaO6 pentagonal pyramids, corners with two equivalent AsO4 tetrahedra, edges with two equivalent NaO6 octahedra, edges with two equivalent NaO6 pentagonal pyramids, and edges with two equivalent AsO4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. There are a spread of Na–O bond distances ranging from 2.39–2.57 Å. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.37–2.71 Å. Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share a cornercorner with one NaO6 octahedra, corners with two equivalent NbO6 octahedra, corners with three equivalent AsO4 tetrahedra, and edges with three equivalent NaO6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 40–64°. There are a spread of Nb–O bond distances ranging from 1.81–2.26 Å. As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one NaO6 octahedra, corners with three equivalent NbO6 octahedra, corners with four equivalent NaO6 pentagonal pyramids, and an edgeedge with one NaO6 octahedra. The corner-sharing octahedra tilt angles range from 39–63°. There are a spread of As–O bond distances ranging from 1.69–1.75 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Na1+ and one Nb5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Nb5+, and one As5+ atom. In the third O2- site, O2- is bonded to three Na1+ and one As5+ atom to form a mixture of distorted corner and edge-sharing ONa3As trigonal pyramids. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+ and two equivalent Nb5+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na1+, one Nb5+, and one As5+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Na1+, one Nb5+, and one As5+ atom.