DOE OSTI2020
Ca4N2(CN2) crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to five N3- atoms to form distorted CaN5 square pyramids that share a cornercorner with one CaN6 octahedra, corners with four equivalent CaN5 trigonal bipyramids, corners with four equivalent CaN4 trigonal pyramids, edges with two equivalent CaN6 octahedra, edges with two equivalent CaN5 square pyramids, and edges with two equivalent CaN5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 11°. There are a spread of Ca–N bond distances ranging from 2.35–2.76 Å. In the second Ca2+ site, Ca2+ is bonded to five N3- atoms to form distorted CaN5 trigonal bipyramids that share corners with four equivalent CaN5 square pyramids, corners with three equivalent CaN4 trigonal pyramids, edges with two equivalent CaN6 octahedra, edges with two equivalent CaN5 square pyramids, and edges with two equivalent CaN5 trigonal bipyramids. There are a spread of Ca–N bond distances ranging from 2.39–2.65 Å. In the third Ca2+ site, Ca2+ is bonded to six N3- atoms to form CaN6 octahedra that share a cornercorner with one CaN5 square pyramid, corners with three equivalent CaN4 trigonal pyramids, edges with four equivalent CaN6 octahedra, edges with two equivalent CaN5 square pyramids, edges with two equivalent CaN5 trigonal bipyramids, and edges with three equivalent CaN4 trigonal pyramids. There are a spread of Ca–N bond distances ranging from 2.50–2.72 Å. In the fourth Ca2+ site, Ca2+ is bonded to four N3- atoms to form distorted CaN4 trigonal pyramids that share corners with three equivalent CaN6 octahedra, corners with four equivalent CaN5 square pyramids, corners with three equivalent CaN5 trigonal bipyramids, corners with two equivalent CaN4 trigonal pyramids, and edges with three equivalent CaN6 octahedra. The corner-sharing octahedral tilt angles are 6°. There are a spread of Ca–N bond distances ranging from 2.35–2.53 Å. C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.24 Å) and one longer (1.25 Å) C–N bond length. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded to six Ca2+ atoms to form NCa6 octahedra that share corners with three equivalent NCa6 octahedra, a cornercorner with one NCa4C trigonal bipyramid, edges with four NCa6 octahedra, and edges with two equivalent NCa4C trigonal bipyramids. The corner-sharing octahedra tilt angles range from 7–54°. In the second N3- site, N3- is bonded in a 1-coordinate geometry to four Ca2+ and one C4+ atom. In the third N3- site, N3- is bonded to four Ca2+ and one C4+ atom to form distorted NCa4C trigonal bipyramids that share corners with three NCa6 octahedra, corners with two equivalent NCa4C trigonal bipyramids, and edges with five NCa6 octahedra. The corner-sharing octahedra tilt angles range from 5–78°. In the fourth N3- site, N3- is bonded to six Ca2+ atoms to form NCa6 octahedra that share corners with three equivalent NCa6 octahedra, corners with two equivalent NCa4C trigonal bipyramids, edges with six NCa6 octahedra, and edges with three equivalent NCa4C trigonal bipyramids. The corner-sharing octahedra tilt angles range from 7–54°.