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Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Cr3Al2(SiO4)3 is Esseneite-like structured and crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Cr2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.23 Å) and four longer (2.47 Å) Cr–O bond lengths. Al3+ is bonded to six equivalent O2- atoms to form AlO6 octahedra that share corners with six equivalent SiO4 tetrahedra. All Al–O bond lengths are 1.91 Å. Si4+ is bonded to four equivalent O2- atoms to form SiO4 tetrahedra that share corners with four equivalent AlO6 octahedra. The corner-sharing octahedral tilt angles are 46°. All Si–O bond lengths are 1.66 Å. O2- is bonded in a 4-coordinate geometry to two equivalent Cr2+, one Al3+, and one Si4+ atom.
BaCr(Si2O5)2 crystallizes in the tetragonal P4/ncc space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.76 Å) and four longer (2.99 Å) Ba–O bond lengths. Cr2+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. All Cr–O bond lengths are 2.04 Å. Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.65 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Ba2+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+, one Cr2+, and one Si4+ atom.
MgCr(SiO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Mg2+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Mg–O bond distances ranging from 1.97–2.05 Å. Cr2+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 2.06–2.40 Å. There are two 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 CrO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–64°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent CrO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–66°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Cr2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Mg2+, one Cr2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+, two equivalent Cr2+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+, two equivalent Cr2+, and one Si4+ atom.