DOI: 10.17188/1673964
title: Materials Data on Ca2MgAl2(SiO4)3 by Materials Project

description: Ca2MgAl2(SiO4)3 is Esseneite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.37–2.75 Å. In the second Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.32–2.74 Å. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five SiO4 tetrahedra, and edges with two equivalent AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.18 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with two equivalent AlO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 36–68°. There are a spread of Al–O bond distances ranging from 1.75–1.80 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four SiO4 tetrahedra, and edges with two equivalent MgO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.08 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one MgO6 octahedra, corners with two equivalent AlO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–61°. There are a spread of Si–O bond distances ranging from 1.62–1.70 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two equivalent MgO6 octahedra, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 35–61°. There are a spread of Si–O bond distances ranging from 1.60–1.70 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two equivalent MgO6 octahedra, and corners with two equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 40–61°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+, one Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded to one Ca2+, one Mg2+, and two Al3+ atoms to form distorted edge-sharing OCaMgAl2 tetrahedra. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Mg2+, one Al3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded to one Ca2+, one Mg2+, one Al3+, and one Si4+ atom to form distorted edge-sharing OCaMgAlSi tetrahedra. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Mg2+, one Al3+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+ and two Al3+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Al3+, and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Mg2+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Mg2+, and one Si4+ atom.