DOI: 10.17188/1272766
title: Materials Data on Ca7NbSi2N9 by Materials Project

description: Ca7NbSi2N9 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six N3- atoms. There are a spread of Ca–N bond distances ranging from 2.44–2.99 Å. In the second Ca2+ site, Ca2+ is bonded to six N3- atoms to form distorted CaN6 octahedra that share corners with two equivalent CaN6 octahedra, a cornercorner with one CaN5 square pyramid, a cornercorner with one NbN5 square pyramid, corners with two SiN4 tetrahedra, edges with five CaN6 octahedra, an edgeedge with one CaN5 square pyramid, edges with two equivalent NbN5 square pyramids, and an edgeedge with one SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 24–49°. There are a spread of Ca–N bond distances ranging from 2.35–2.74 Å. In the third Ca2+ site, Ca2+ is bonded to five N3- atoms to form CaN5 square pyramids that share corners with four CaN6 octahedra, a cornercorner with one NbN5 square pyramid, edges with four CaN6 octahedra, an edgeedge with one NbN5 square pyramid, and an edgeedge with one SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 12–76°. There are a spread of Ca–N bond distances ranging from 2.37–2.41 Å. In the fourth Ca2+ site, Ca2+ is bonded to six N3- atoms to form distorted CaN6 octahedra that share corners with two equivalent CaN6 octahedra, a cornercorner with one CaN5 square pyramid, corners with two equivalent NbN5 square pyramids, corners with three SiN4 tetrahedra, edges with four CaN6 octahedra, an edgeedge with one CaN5 square pyramid, and edges with two SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 24–49°. There are a spread of Ca–N bond distances ranging from 2.46–2.72 Å. Nb5+ is bonded to five N3- atoms to form distorted NbN5 square pyramids that share corners with six CaN6 octahedra, a cornercorner with one CaN5 square pyramid, edges with four equivalent CaN6 octahedra, an edgeedge with one CaN5 square pyramid, and an edgeedge with one SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 11–76°. There are a spread of Nb–N bond distances ranging from 1.91–2.31 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four N3- atoms to form SiN4 tetrahedra that share corners with six CaN6 octahedra, edges with two equivalent CaN6 octahedra, an edgeedge with one CaN5 square pyramid, and an edgeedge with one SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 12–42°. There is two shorter (1.75 Å) and two longer (1.82 Å) Si–N bond length. In the second Si4+ site, Si4+ is bonded to four N3- atoms to form SiN4 tetrahedra that share corners with four CaN6 octahedra, edges with four CaN6 octahedra, an edgeedge with one NbN5 square pyramid, and an edgeedge with one SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 3–42°. There is two shorter (1.73 Å) and two longer (1.80 Å) Si–N bond length. There are six inequivalent N3- sites. In the first N3- site, N3- is bonded to five Ca2+ and one Si4+ atom to form distorted NCa5Si octahedra that share corners with five NCa5Nb octahedra and edges with seven NCa5Si octahedra. The corner-sharing octahedra tilt angles range from 12–73°. In the second N3- site, N3- is bonded in a 2-coordinate geometry to four Ca2+ and two Si4+ atoms. In the third N3- site, N3- is bonded to five Ca2+ and one Nb5+ atom to form a mixture of distorted edge and corner-sharing NCa5Nb octahedra. The corner-sharing octahedra tilt angles range from 7–25°. In the fourth N3- site, N3- is bonded to four Ca2+, one Nb5+, and one Si4+ atom to form a mixture of distorted edge and corner-sharing NCa4NbSi octahedra. The corner-sharing octahedra tilt angles range from 13–73°. In the fifth N3- site, N3- is bonded to five Ca2+ and one Nb5+ atom to form a mixture of edge and corner-sharing NCa5Nb octahedra. The corner-sharing octahedra tilt angles range from 7–13°. In the sixth N3- site, N3- is bonded in a 2-coordinate geometry to four Ca2+ and two Si4+ atoms.