Materials Data on MgAlCr3FeO8 by Materials Project

MgCr3FeAlO8 is Spinel-derived structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent AlO6 octahedra and corners with nine equivalent CrO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is one shorter (1.97 Å) and three longer (2.01 Å) Mg–O bond length. Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent FeO4 tetrahedra, edges with two equivalent AlO6 octahedra, and edges with four equivalent CrO6 octahedra. There are one shorter (2.02 Å) and five longer (2.03 Å) Cr–O bond lengths. Fe2+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with three equivalent AlO6 octahedra and corners with nine equivalent CrO6 octahedra. The corner-sharing octahedra tilt angles range from 55–62°. There is one shorter (1.96 Å) and three longer (2.03 Å) Fe–O bond length. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent FeO4 tetrahedra, and edges with six equivalent CrO6 octahedra. There is three shorter (1.94 Å) and three longer (1.95 Å) Al–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Cr3+, one Fe2+, and one Al3+ atom. In the second O2- site, O2- is bonded to three equivalent Cr3+ and one Fe2+ atom to form distorted corner-sharing OCr3Fe trigonal pyramids. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+, two equivalent Cr3+, and one Al3+ atom. In the fourth O2- site, O2- is bonded to one Mg2+ and three equivalent Cr3+ atoms to form distorted corner-sharing OMgCr3 trigonal pyramids.