Materials Data on Ca7SiN6 by Materials Project

Abstract

Ca7SiN6 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 5-coordinate geometry to five N3- atoms. There are a spread of Ca–N bond distances ranging from 2.38–2.92 Å. In the second Ca2+ site, Ca2+ is bonded to five N3- atoms to form distorted CaN5 trigonal bipyramids that share a cornercorner with one SiN4 tetrahedra, corners with six equivalent CaN5 trigonal bipyramids, an edgeedge with one SiN4 tetrahedra, and edges with three CaN5 trigonal bipyramids. There are a spread of Ca–N bond distances ranging from 2.36–2.95 Å. In the third Ca2+ site, Ca2+ is bonded to five N3- atoms to form distorted CaN5 trigonal bipyramids that share a cornercorner with one SiN4 tetrahedra, corners with six equivalent CaN5 trigonal bipyramids, an edgeedge with one SiN4 tetrahedra, and edges with three CaN5 trigonal bipyramids. There are a spread of Ca–N bond distances ranging from 2.34–2.73 Å. In the fourth Ca2+ site, Ca2+ is bonded in a 4-coordinate geometry to four N3- atoms. There are two shorter (2.46 Å) and two longer (2.57 Å) Ca–N bond lengths. Si4+ is bonded to four N3- atoms to form SiN4 tetrahedra that share corners with four CaN5 trigonal bipyramids and edges with four CaN5 trigonal bipyramids. There is two shorter (1.78 Å) and two longer (1.80 Å) Si–N bond length. There are three 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 two equivalent NCa5Si octahedra, corners with four equivalent NCa6 pentagonal pyramids, an edgeedge with one NCa5Si octahedra, and edges with two equivalent NCa6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 68°. In the second N3- site, N3- is bonded to six Ca2+ atoms to form distorted NCa6 pentagonal pyramids that share corners with four equivalent NCa5Si octahedra, edges with two equivalent NCa5Si octahedra, and edges with three equivalent NCa6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 25–72°. In the third N3- site, N3- is bonded in a 7-coordinate geometry to six Ca2+ and one Si4+ atom.