DOE OSTI2020
Ba9(TaN6)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are nine inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 7-coordinate geometry to seven N+2.33- atoms. There are a spread of Ba–N bond distances ranging from 2.82–3.32 Å. In the second Ba2+ site, Ba2+ is bonded to six N+2.33- atoms to form distorted BaN6 octahedra that share a cornercorner with one BaN6 octahedra, a cornercorner with one BaN5 square pyramid, a cornercorner with one TaN4 tetrahedra, a cornercorner with one BaN5 trigonal bipyramid, edges with three BaN6 octahedra, an edgeedge with one BaN5 square pyramid, an edgeedge with one TaN4 tetrahedra, and edges with two BaN5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 38°. There are a spread of Ba–N bond distances ranging from 2.54–3.17 Å. In the third Ba2+ site, Ba2+ is bonded to six N+2.33- atoms to form distorted BaN6 octahedra that share corners with two equivalent BaN6 octahedra, a cornercorner with one TaN4 tetrahedra, edges with two equivalent BaN6 octahedra, edges with two equivalent BaN5 square pyramids, an edgeedge with one TaN4 tetrahedra, and edges with two BaN5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 12–19°. There are a spread of Ba–N bond distances ranging from 2.76–3.13 Å. In the fourth Ba2+ site, Ba2+ is bonded to five N+2.33- atoms to form distorted BaN5 trigonal bipyramids that share corners with three equivalent BaN5 square pyramids, corners with four TaN4 tetrahedra, and edges with four BaN6 octahedra. There are a spread of Ba–N bond distances ranging from 2.67–3.21 Å. In the fifth Ba2+ site, Ba2+ is bonded in a 4-coordinate geometry to seven N+2.33- atoms. There are a spread of Ba–N bond distances ranging from 2.61–3.34 Å. In the sixth Ba2+ site, Ba2+ is bonded to six N+2.33- atoms to form distorted BaN6 octahedra that share corners with three BaN6 octahedra, a cornercorner with one BaN5 square pyramid, a cornercorner with one TaN4 tetrahedra, a cornercorner with one BaN5 trigonal bipyramid, edges with two BaN6 octahedra, an edgeedge with one BaN5 square pyramid, edges with two TaN4 tetrahedra, and edges with two equivalent BaN5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 12–38°. There are a spread of Ba–N bond distances ranging from 2.88–3.20 Å. In the seventh Ba2+ site, Ba2+ is bonded to five N+2.33- atoms to form distorted BaN5 trigonal bipyramids that share corners with two BaN6 octahedra, a cornercorner with one BaN5 square pyramid, corners with four TaN4 tetrahedra, edges with two BaN6 octahedra, and an edgeedge with one BaN5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 17–99°. There are a spread of Ba–N bond distances ranging from 2.70–3.08 Å. In the eighth Ba2+ site, Ba2+ is bonded in a 7-coordinate geometry to seven N+2.33- atoms. There are a spread of Ba–N bond distances ranging from 2.69–3.21 Å. In the ninth Ba2+ site, Ba2+ is bonded to five N+2.33- atoms to form distorted BaN5 square pyramids that share corners with two BaN6 octahedra, corners with two TaN4 tetrahedra, corners with four BaN5 trigonal bipyramids, edges with four BaN6 octahedra, an edgeedge with one BaN5 square pyramid, and an edgeedge with one TaN4 tetrahedra. The corner-sharing octahedra tilt angles range from 78–87°. There are a spread of Ba–N bond distances ranging from 2.72–3.23 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to four N+2.33- atoms to form TaN4 tetrahedra that share corners with three BaN6 octahedra, a cornercorner with one BaN5 square pyramid, corners with four BaN5 trigonal bipyramids, an edgeedge with one BaN6 octahedra, and an edgeedge with one BaN5 square pyramid. The corner-sharing octahedra tilt angles range from 55–84°. There are a spread of Ta–N bond distances ranging from 1.97–2.02 Å. In the second Ta5+ site, Ta5+ is bonded to four N+2.33- atoms to form TaN4 tetrahedra that share a cornercorner with one BaN5 square pyramid, corners with four BaN5 trigonal bipyramids, and edges with three BaN6 octahedra. There are a spread of Ta–N bond distances ranging from 1.95–2.00 Å. There are twelve inequivalent N+2.33- sites. In the first N+2.33- site, N+2.33- is bonded in a 1-coordinate geometry to four Ba2+ and one Ta5+ atom. In the second N+2.33- site, N+2.33- is bonded to five Ba2+ and one Ta5+ atom to form distorted NBa5Ta octahedra that share corners with two equivalent NBa6 octahedra and edges with three NBa5Ta octahedra. The corner-sharing octahedra tilt angles range from 20–24°. In the third N+2.33- site, N+2.33- is bonded in a 5-coordinate geometry to four Ba2+ and one N+2.33- atom. The N–N bond length is 1.19 Å. In the fourth N+2.33- site, N+2.33- is bonded in a distorted rectangular see-saw-like geometry to two Ba2+ and two N+2.33- atoms. The N–N bond length is 1.19 Å. In the fifth N+2.33- site, N+2.33- is bonded in a 5-coordinate geometry to four Ba2+ and one Ta5+ atom. In the sixth N+2.33- site, N+2.33- is bonded in a 6-coordinate geometry to five Ba2+ and one Ta5+ atom. In the seventh N+2.33- site, N+2.33- is bonded in a 6-coordinate geometry to four Ba2+ and one N+2.33- atom. In the eighth N+2.33- site, N+2.33- is bonded in a 6-coordinate geometry to five Ba2+ and one Ta5+ atom. In the ninth N+2.33- site, N+2.33- is bonded in a 6-coordinate geometry to five Ba2+ and one Ta5+ atom. In the tenth N+2.33- site, N+2.33- is bonded to six Ba2+ atoms to form a mixture of corner and edge-sharing NBa6 octahedra. The corner-sharing octahedra tilt angles range from 20–24°. In the eleventh N+2.33- site, N+2.33- is bonded in a 1-coordinate geometry to five Ba2+ and one Ta5+ atom. In the twelfth N+2.33- site, N+2.33- is bonded in a 1-coordinate geometry to five Ba2+ and one Ta5+ atom.