DOI: 10.17188/1306407
title: Materials Data on Na9Cu2O7 by Materials Project

description: Na9Cu2O7 crystallizes in the orthorhombic Pca2_1 space group. The structure is three-dimensional. there are nine inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share a cornercorner with one NaO5 square pyramid, a cornercorner with one NaO4 tetrahedra, corners with three equivalent CuO4 tetrahedra, a cornercorner with one NaO5 trigonal bipyramid, an edgeedge with one NaO4 tetrahedra, a faceface with one NaO5 square pyramid, and a faceface with one NaO5 trigonal bipyramid. There are a spread of Na–O bond distances ranging from 2.37–2.61 Å. In the second Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.33–2.85 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 2.33–2.99 Å. In the fourth Na1+ site, Na1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Na–O bond distances ranging from 2.29–2.70 Å. In the fifth Na1+ site, Na1+ is bonded to five O2- atoms to form distorted NaO5 trigonal bipyramids that share a cornercorner with one NaO6 octahedra, a cornercorner with one NaO5 square pyramid, a cornercorner with one CuO4 tetrahedra, corners with three equivalent NaO4 tetrahedra, corners with two equivalent NaO5 trigonal bipyramids, an edgeedge with one NaO5 square pyramid, edges with two equivalent CuO4 tetrahedra, and a faceface with one NaO6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are a spread of Na–O bond distances ranging from 2.29–2.55 Å. In the sixth Na1+ site, Na1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–2.71 Å. In the seventh Na1+ site, Na1+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.31 Å) and one longer (2.38 Å) Na–O bond lengths. In the eighth Na1+ site, Na1+ is bonded to five O2- atoms to form distorted NaO5 square pyramids that share a cornercorner with one NaO6 octahedra, corners with two equivalent NaO5 square pyramids, a cornercorner with one NaO4 tetrahedra, corners with two equivalent CuO4 tetrahedra, a cornercorner with one NaO5 trigonal bipyramid, an edgeedge with one NaO5 trigonal bipyramid, and a faceface with one NaO6 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of Na–O bond distances ranging from 2.37–2.65 Å. In the ninth Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share a cornercorner with one NaO6 octahedra, a cornercorner with one NaO5 square pyramid, a cornercorner with one CuO4 tetrahedra, corners with three equivalent NaO5 trigonal bipyramids, an edgeedge with one NaO6 octahedra, and an edgeedge with one CuO4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. There are a spread of Na–O bond distances ranging from 2.32–2.37 Å. There are two inequivalent Cu+2.50+ sites. In the first Cu+2.50+ site, Cu+2.50+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with three equivalent NaO6 octahedra, corners with two equivalent NaO5 square pyramids, a cornercorner with one NaO4 tetrahedra, a cornercorner with one NaO5 trigonal bipyramid, an edgeedge with one NaO4 tetrahedra, and edges with two equivalent NaO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 40–56°. There are a spread of Cu–O bond distances ranging from 1.92–2.02 Å. In the second Cu+2.50+ site, Cu+2.50+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of Cu–O bond distances ranging from 1.84–1.91 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 7-coordinate geometry to six Na1+ and one Cu+2.50+ atom. In the second O2- site, O2- is bonded in a 7-coordinate geometry to six Na1+ and one Cu+2.50+ atom. In the third O2- site, O2- is bonded in a 8-coordinate geometry to seven Na1+ and one Cu+2.50+ atom. In the fourth O2- site, O2- is bonded in a 7-coordinate geometry to six Na1+ and one Cu+2.50+ atom. In the fifth O2- site, O2- is bonded in a 7-coordinate geometry to six Na1+ and one Cu+2.50+ atom. In the sixth O2- site, O2- is bonded in a 7-coordinate geometry to six Na1+ and one Cu+2.50+ atom. In the seventh O2- site, O2- is bonded in a 7-coordinate geometry to six Na1+ and one Cu+2.50+ atom.