Materials Data on Mg3Bi2O7 by Materials Project
Mg3Bi2O7 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 trigonal pyramids that share corners with eight equivalent BiO6 octahedra and corners with two equivalent MgO4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 64–82°. There are two shorter (2.03 Å) and two longer (2.06 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded in a 4-coordinate geometry to five O2- atoms. There are a spread of Mg–O bond distances ranging from 2.04–2.69 Å. Bi4+ is bonded to six O2- atoms to form BiO6 octahedra that share corners with five equivalent BiO6 octahedra and corners with four equivalent MgO4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 47–64°. There are a spread of Bi–O bond distances ranging from 2.20–2.41 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Mg2+ and one Bi4+ atom to form distorted corner-sharing OMg3Bi tetrahedra. In the second O2- site, O2- is bonded in a trigonal planar geometry to one Mg2+ and two equivalent Bi4+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Mg2+ and two equivalent Bi4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Mg2+ and two equivalent Bi4+ atoms.