MgNb5O9 is (Cubic) Perovskite-like structured and crystallizes in the trigonal P-3m1 space group. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Nb(3)O6 octahedra, faces with two equivalent Nb(1)O12 cuboctahedra, and faces with six equivalent Nb(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 3°. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form NbO12 cuboctahedra that share corners with six equivalent Nb(1)O12 cuboctahedra, corners with six equivalent Nb(2)O12 cuboctahedra, faces with six equivalent Nb(2)O12 cuboctahedra, faces with two equivalent Mg(1)O6 octahedra, and faces with six equivalent Nb(3)O6 octahedra. In the second Nb site, Nb(2) is bonded to three equivalent O(1) and nine equivalent O(2) atoms to form NbO12 cuboctahedra that share corners with three equivalent Nb(1)O12 cuboctahedra, corners with nine equivalent Nb(2)O12 cuboctahedra, faces with three equivalent Nb(1)O12 cuboctahedra, faces with three equivalent Nb(2)O12 cuboctahedra, faces with three equivalent Mg(1)O6 octahedra, and faces with five equivalent Nb(3)O6 octahedra. In the third Nb site, Nb(3) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NbO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Nb(3)O6 octahedra, faces with three equivalent Nb(1)O12 cuboctahedra, and faces with five equivalent Nb(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-3°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent Nb(1), two equivalent Nb(2), and two equivalent Nb(3) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to one Mg(1), one Nb(1), one Nb(3), and three equivalent Nb(2) atoms.
MgNb5O9 is (Cubic) Perovskite-like structured and crystallizes in the trigonal P-3m1 space group. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Nb(3)O6 octahedra, faces with two equivalent Nb(1)O12 cuboctahedra, and faces with six equivalent Nb(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 3°. All Mg(1)-O(2) bond lengths are 1.97 Å. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form NbO12 cuboctahedra that share corners with six equivalent Nb(1)O12 cuboctahedra, corners with six equivalent Nb(2)O12 cuboctahedra, faces with six equivalent Nb(2)O12 cuboctahedra, faces with two equivalent Mg(1)O6 octahedra, and faces with six equivalent Nb(3)O6 octahedra. All Nb(1)-O(1) bond lengths are 2.81 Å. All Nb(1)-O(2) bond lengths are 2.79 Å. In the second Nb site, Nb(2) is bonded to three equivalent O(1) and nine equivalent O(2) atoms to form NbO12 cuboctahedra that share corners with three equivalent Nb(1)O12 cuboctahedra, corners with nine equivalent Nb(2)O12 cuboctahedra, faces with three equivalent Nb(1)O12 cuboctahedra, faces with three equivalent Nb(2)O12 cuboctahedra, faces with three equivalent Mg(1)O6 octahedra, and faces with five equivalent Nb(3)O6 octahedra. All Nb(2)-O(1) bond lengths are 2.83 Å. There are three shorter (2.79 Å) and six longer (2.81 Å) Nb(2)-O(2) bond lengths. In the third Nb site, Nb(3) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NbO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent Nb(3)O6 octahedra, faces with three equivalent Nb(1)O12 cuboctahedra, and faces with five equivalent Nb(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-3°. All Nb(3)-O(1) bond lengths are 2.05 Å. All Nb(3)-O(2) bond lengths are 1.94 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent Nb(1), two equivalent Nb(2), and two equivalent Nb(3) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to one Mg(1), one Nb(1), one Nb(3), and three equivalent Nb(2) atoms.