DOI: 10.17188/1206536
title: Materials Data on MgAl2O4 by Materials Project

description: MgAl2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–61°. There is three shorter (1.92 Å) and one longer (2.01 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–63°. There is three shorter (1.93 Å) and one longer (1.97 Å) Mg–O bond length. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.00 Å) and three longer (2.10 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. There is one shorter (1.93 Å) and three longer (1.96 Å) Mg–O bond length. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six AlO6 octahedra. There are three shorter (2.03 Å) and three longer (2.08 Å) Mg–O bond lengths. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There is one shorter (1.95 Å) and three longer (1.96 Å) Mg–O bond length. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There is three shorter (1.97 Å) and one longer (2.00 Å) Mg–O bond length. In the eighth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–62°. There is three shorter (1.96 Å) and one longer (2.01 Å) Mg–O bond length. There are eight inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.04 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.07 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.95 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There is three shorter (1.84 Å) and one longer (1.85 Å) Al–O bond length. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.91 Å) and three longer (1.95 Å) Al–O bond length. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.98 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.92 Å) and three longer (1.94 Å) Al–O bond length. In the eighth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is three shorter (1.83 Å) and one longer (1.86 Å) Al–O bond length. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the fifth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 tetrahedra. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form corner-sharing OMgAl3 tetrahedra.