DOI: 10.17188/1284065
title: Materials Data on Sr2Er2Al3Si5N11O3 by Materials Project

description: Sr2Er2Al3Si5N11O3 crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to three equivalent N3- and three equivalent O2- atoms to form SrN3O3 octahedra that share corners with three equivalent AlN4 tetrahedra and corners with nine SiN4 tetrahedra. All Sr–N bond lengths are 2.37 Å. All Sr–O bond lengths are 2.57 Å. In the second Sr2+ site, Sr2+ is bonded to six N3- atoms to form SrN6 octahedra that share corners with six equivalent AlN4 tetrahedra and corners with six SiN2O2 tetrahedra. There are three shorter (2.41 Å) and three longer (2.47 Å) Sr–N bond lengths. There are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded in a 3-coordinate geometry to three equivalent N3- atoms. All Er–N bond lengths are 2.27 Å. In the second Er3+ site, Er3+ is bonded in a distorted T-shaped geometry to three equivalent N3- atoms. All Er–N bond lengths are 2.44 Å. Al3+ is bonded to four N3- atoms to form AlN4 tetrahedra that share corners with three SrN3O3 octahedra, corners with two SiN4 tetrahedra, and corners with four equivalent AlN4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–60°. There are a spread of Al–N bond distances ranging from 1.81–2.01 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four N3- atoms to form SiN4 tetrahedra that share corners with three equivalent SrN6 octahedra, corners with three equivalent AlN4 tetrahedra, and corners with three equivalent SiN2O2 tetrahedra. The corner-sharing octahedral tilt angles are 58°. There is three shorter (1.73 Å) and one 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 three equivalent SrN3O3 octahedra, corners with three equivalent AlN4 tetrahedra, and corners with three equivalent SiN2O2 tetrahedra. The corner-sharing octahedral tilt angles are 51°. There is three shorter (1.68 Å) and one longer (1.99 Å) Si–N bond length. In the third Si4+ site, Si4+ is bonded to two N3- and two equivalent O2- atoms to form SiN2O2 tetrahedra that share corners with three SrN3O3 octahedra and corners with six SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 62–65°. There is one shorter (1.64 Å) and one longer (2.02 Å) Si–N bond length. Both Si–O bond lengths are 1.72 Å. There are five inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to one Sr2+, one Al3+, and one Si4+ atom. In the second N3- site, N3- is bonded to three equivalent Al3+ and one Si4+ atom to form distorted corner-sharing NAl3Si trigonal pyramids. In the third N3- site, N3- is bonded in a tetrahedral geometry to four Si4+ atoms. In the fourth N3- site, N3- is bonded in a trigonal planar geometry to one Sr2+ and two Si4+ atoms. In the fifth N3- site, N3- is bonded to one Sr2+, two Er3+, and two equivalent Al3+ atoms to form NSrEr2Al2 trigonal bipyramids that share corners with two equivalent NAl3Si trigonal pyramids and edges with four equivalent NSrEr2Al2 trigonal bipyramids. O2- is bonded in a trigonal planar geometry to one Sr2+ and two equivalent Si4+ atoms.