DOE OSTI2020
Ca3N2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are five inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to five N3- atoms to form distorted CaN5 square pyramids that share corners with seven CaN4 tetrahedra, corners with two equivalent CaN4 trigonal pyramids, edges with two equivalent CaN6 octahedra, edges with two equivalent CaN5 square pyramids, edges with three CaN4 tetrahedra, and edges with three equivalent CaN4 trigonal pyramids. There are a spread of Ca–N bond distances ranging from 2.35–2.71 Å. In the second Ca2+ site, Ca2+ is bonded to four N3- atoms to form CaN4 trigonal pyramids that share a cornercorner with one CaN6 octahedra, corners with two equivalent CaN5 square pyramids, corners with nine CaN4 tetrahedra, corners with two equivalent CaN4 trigonal pyramids, edges with three equivalent CaN5 square pyramids, and edges with two equivalent CaN4 trigonal pyramids. The corner-sharing octahedral tilt angles are 37°. There are a spread of Ca–N bond distances ranging from 2.40–2.63 Å. In the third Ca2+ site, Ca2+ is bonded to four N3- atoms to form CaN4 tetrahedra that share a cornercorner with one CaN6 octahedra, corners with five equivalent CaN5 square pyramids, corners with four CaN4 tetrahedra, corners with three equivalent CaN4 trigonal pyramids, edges with two equivalent CaN6 octahedra, an edgeedge with one CaN5 square pyramid, and edges with two equivalent CaN4 tetrahedra. The corner-sharing octahedral tilt angles are 46°. There are a spread of Ca–N bond distances ranging from 2.34–2.51 Å. In the fourth Ca2+ site, Ca2+ is bonded to four N3- atoms to form distorted CaN4 tetrahedra that share corners with two equivalent CaN6 octahedra, corners with two equivalent CaN5 square pyramids, corners with four CaN4 tetrahedra, corners with six equivalent CaN4 trigonal pyramids, an edgeedge with one CaN6 octahedra, edges with two equivalent CaN5 square pyramids, and an edgeedge with one CaN4 tetrahedra. The corner-sharing octahedral tilt angles are 12°. There are a spread of Ca–N bond distances ranging from 2.37–2.72 Å. In the fifth Ca2+ site, Ca2+ is bonded to six N3- atoms to form CaN6 octahedra that share corners with six CaN4 tetrahedra, corners with two equivalent CaN4 trigonal pyramids, edges with two equivalent CaN6 octahedra, edges with four equivalent CaN5 square pyramids, and edges with six CaN4 tetrahedra. There are four shorter (2.68 Å) and two longer (2.80 Å) Ca–N bond lengths. There are three inequivalent N3- sites. In the first N3- site, N3- is bonded in a 7-coordinate geometry to seven Ca2+ atoms. In the second N3- site, N3- is bonded to six Ca2+ atoms to form a mixture of corner and edge-sharing NCa6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the third N3- site, N3- is bonded in a 7-coordinate geometry to seven Ca2+ atoms.