Materials Data on Mg2Al2O5 by Materials Project
Mg2Al2O5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Mg–O bond lengths are 2.27 Å. In the second Mg2+ site, Mg2+ is bonded to twelve O2- atoms to form distorted MgO12 cuboctahedra that share corners with four equivalent MgO12 cuboctahedra, faces with four equivalent MgO12 cuboctahedra, and faces with eight equivalent AlO5 square pyramids. There are four shorter (2.55 Å) and eight longer (2.79 Å) Mg–O bond lengths. Al3+ is bonded to five O2- atoms to form AlO5 square pyramids that share corners with five equivalent AlO5 square pyramids and faces with four equivalent MgO12 cuboctahedra. There is one shorter (1.79 Å) and four longer (1.83 Å) Al–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to four Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded to four equivalent Mg2+ and two equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OMg4Al2 octahedra. The corner-sharing octahedral tilt angles are 0°.