Materials Data on MgAl2O4 by Materials Project

Abstract

MgAl2O4 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are three inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Mg–O bond lengths are 2.11 Å. In the second Mg2+ site, Mg2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Mg–O bond lengths are 2.11 Å. In the third Mg2+ site, Mg2+ is bonded in a distorted trigonal planar geometry to nine O2- atoms. There are three shorter (2.27 Å) and six longer (2.67 Å) Mg–O bond lengths. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Al–O bond distances ranging from 1.90–1.98 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Al–O bond distances ranging from 1.89–1.98 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Mg2+ and three Al3+ atoms to form distorted OMg2Al3 trigonal bipyramids that share corners with three equivalent OMgAl3 tetrahedra, corners with four equivalent OMg2Al3 trigonal bipyramids, an edgeedge with one OMgAl3 tetrahedra, and edges with six OMg2Al3 trigonal bipyramids. In the second O2- site, O2- is bonded to two equivalent Mg2+ and three Al3+ atoms to form distorted OMg2Al3 trigonal bipyramids that share corners with four equivalent OMgAl3 tetrahedra, corners with four equivalent OMg2Al3 trigonal bipyramids, and edges with six OMg2Al3 trigonal bipyramids. In the third O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 tetrahedra that share corners with four equivalent OMgAl3 tetrahedra, corners with seven OMg2Al3 trigonal bipyramids, and an edgeedge with one OMg2Al3 trigonal bipyramid. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Mg2+ and three Al3+ atoms.