Materials Data on Ca11N8 by Materials Project
Ca11N8 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a distorted trigonal planar geometry to three equivalent N+2.75- atoms. There are one shorter (2.38 Å) and two longer (2.41 Å) Ca–N bond lengths. In the second Ca2+ site, Ca2+ is bonded to five N+2.75- atoms to form CaN5 trigonal bipyramids that share corners with two equivalent CaN4 tetrahedra, corners with two equivalent CaN5 trigonal bipyramids, and edges with four equivalent CaN4 tetrahedra. There are a spread of Ca–N bond distances ranging from 2.46–2.72 Å. In the third Ca2+ site, Ca2+ is bonded to four N+2.75- atoms to form CaN4 tetrahedra that share corners with four equivalent CaN4 tetrahedra, a cornercorner with one CaN5 trigonal bipyramid, and edges with two equivalent CaN5 trigonal bipyramids. There are a spread of Ca–N bond distances ranging from 2.38–2.43 Å. In the fourth Ca2+ site, Ca2+ is bonded in a square co-planar geometry to four equivalent N+2.75- atoms. All Ca–N bond lengths are 2.50 Å. There are three inequivalent N+2.75- sites. In the first N+2.75- site, N+2.75- is bonded to six Ca2+ atoms to form a mixture of edge and corner-sharing NCa6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second N+2.75- site, N+2.75- is bonded in a distorted trigonal planar geometry to three Ca2+ atoms. In the third N+2.75- site, N+2.75- is bonded to six Ca2+ atoms to form a mixture of distorted edge and corner-sharing NCa6 octahedra. The corner-sharing octahedra tilt angles range from 2–54°.