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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Mg4Nb2O9 by Materials Project

Mg4Nb2O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six equivalent O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO6 octahedra, corners with six equivalent NbO6 octahedra, edges with three equivalent MgO6 octahedra, and a faceface with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are three shorter (2.09 Å) and three longer (2.17 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 octahedra that share corners with three equivalent NbO6 octahedra, corners with six MgO6 octahedra, edges with three equivalent NbO6 octahedra, and a faceface with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 48–65°. There are three shorter (2.04 Å) and three longer (2.24 Å) Mg–O bond lengths. Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with nine MgO6 octahedra, edges with three equivalent MgO6 octahedra, and a faceface with one NbO6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are three shorter (1.93 Å) and three longer (2.16 Å) Nb–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three Mg2+ and one Nb5+ atom to form a mixture of distorted corner and edge-sharing OMg3Nb trigonal pyramids. In the second O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Nb5+ atoms to form a mixture of distorted corner and edge-sharing OMg2Nb2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgNb2O6 by Materials Project

MgNb2O6 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Mg2+ is bonded to six O2- atoms to form edge-sharing MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.15 Å. Nb5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.83–2.34 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Nb5+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one Nb5+ atom. In the third O2- site, O2- is bonded in a trigonal planar geometry to one Mg2+ and two equivalent Nb5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Nb6O11 by Materials Project

Mg3Nb6O11 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six equivalent O2- atoms to form MgO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six equivalent NbO5 square pyramids. All Mg–O bond lengths are 2.11 Å. 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 equivalent NbO5 square pyramids. The corner-sharing octahedral tilt angles are 60°. There are one shorter (1.99 Å) and three longer (2.02 Å) Mg–O bond lengths. Nb+2.67+ is bonded to five O2- atoms to form NbO5 square pyramids that share corners with six equivalent NbO5 square pyramids, corners with three equivalent MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with two equivalent NbO5 square pyramids. There are a spread of Nb–O bond distances ranging from 2.11–2.25 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a square co-planar geometry to four equivalent Nb+2.67+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Nb+2.67+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to one Mg2+ and three equivalent Nb+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgNb5O9 by Materials Project

MgNb5O9 is (Cubic) Perovskite-like structured and crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Mg2+ is bonded to six equivalent O2- atoms to form MgO6 octahedra that share corners with six equivalent NbO6 octahedra and faces with eight NbO12 cuboctahedra. The corner-sharing octahedral tilt angles are 3°. All Mg–O bond lengths are 1.97 Å. There are three inequivalent Nb+3.20+ sites. In the first Nb+3.20+ site, Nb+3.20+ is bonded to twelve O2- atoms to form NbO12 cuboctahedra that share corners with twelve NbO12 cuboctahedra, faces with six equivalent NbO12 cuboctahedra, faces with two equivalent MgO6 octahedra, and faces with six equivalent NbO6 octahedra. There are six shorter (2.79 Å) and six longer (2.81 Å) Nb–O bond lengths. In the second Nb+3.20+ site, Nb+3.20+ is bonded to twelve O2- atoms to form NbO12 cuboctahedra that share corners with twelve NbO12 cuboctahedra, faces with six NbO12 cuboctahedra, faces with three equivalent MgO6 octahedra, and faces with five equivalent NbO6 octahedra. There are a spread of Nb–O bond distances ranging from 2.79–2.83 Å. In the third Nb+3.20+ site, Nb+3.20+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with three equivalent MgO6 octahedra, corners with three equivalent NbO6 octahedra, and faces with eight NbO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–3°. There is three shorter (1.94 Å) and three longer (2.05 Å) Nb–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to six Nb+3.20+ atoms. In the second O2- site, O2- is bonded in a linear geometry to one Mg2+ and five Nb+3.20+ atoms.

36 MATERIALS SCIENCE↗