Materials Data on Ca5Al2(SiN4)2 by Materials Project
Ca5Si2Al2N8 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six N3- atoms. There are a spread of Ca–N bond distances ranging from 2.39–2.65 Å. In the second Ca2+ site, Ca2+ is bonded in a 4-coordinate geometry to eight N3- atoms. There are a spread of Ca–N bond distances ranging from 2.52–3.04 Å. In the third Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six N3- atoms. There are a spread of Ca–N bond distances ranging from 2.40–2.74 Å. Al3+ is bonded to four N3- atoms to form AlN4 tetrahedra that share corners with two equivalent AlN4 tetrahedra, corners with two equivalent SiN4 tetrahedra, and an edgeedge with one AlN4 tetrahedra. There are a spread of Al–N bond distances ranging from 1.85–1.97 Å. Si4+ is bonded to four N3- atoms to form SiN4 tetrahedra that share corners with two equivalent AlN4 tetrahedra and an edgeedge with one SiN4 tetrahedra. There are a spread of Si–N bond distances ranging from 1.72–1.85 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a 6-coordinate geometry to five Ca2+ and one Si4+ atom. In the second N3- site, N3- is bonded to four Ca2+ and two equivalent Si4+ atoms to form distorted edge-sharing NCa4Si2 octahedra. In the third N3- site, N3- is bonded in a 3-coordinate geometry to three Ca2+, two equivalent Al3+, and one Si4+ atom. In the fourth N3- site, N3- is bonded in a 2-coordinate geometry to four Ca2+ and two equivalent Al3+ atoms.