DOI: 10.17188/1283238
title: Materials Data on Ca2MgAl2(SiO4)3 by Materials Project

description: Ca2MgAl2(SiO4)3 is Esseneite-derived structured and crystallizes in the triclinic P-1 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 2.36–2.76 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 2.34–2.70 Å. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six SiO4 tetrahedra, an edgeedge with one MgO6 octahedra, and an edgeedge with one AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.16 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 corners with three equivalent AlO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–62°. There are a spread of Al–O bond distances ranging from 1.74–1.81 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent AlO4 tetrahedra, corners with three SiO4 tetrahedra, an edgeedge with one MgO6 octahedra, and an edgeedge with one AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–2.10 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 corners with three equivalent MgO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–59°. There are a spread of Si–O bond distances ranging from 1.61–1.70 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, a cornercorner with one AlO4 tetrahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 41–60°. There are a spread of Si–O bond distances ranging from 1.61–1.71 Å. In the third 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, a cornercorner with one AlO4 tetrahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–62°. There are a spread of Si–O bond distances ranging from 1.63–1.68 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+, one Al3+, and one Si4+ atom. 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 3-coordinate geometry to one Ca2+, one Mg2+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two equivalent Mg2+, and one Si4+ atom. 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 in a 3-coordinate geometry to one Ca2+, one Mg2+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ca2+ and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+, one Al3+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+ and two Al3+ atoms. In the eleventh O2- site, O2- is bonded to one Ca2+ and three Al3+ atoms to form distorted edge-sharing OCaAl3 tetrahedra. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Mg2+, one Al3+, and one Si4+ atom.