Mg2La3NbO9 crystallizes in the orthorhombic Immm space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mg(3)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with four equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mg(3)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with two equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-12°. In the third Mg site, Mg(3) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, and faces with four equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-1°. There are two inequivalent La sites. In the first La site, La(1) is bonded to two equivalent O(1), two equivalent O(2), four equivalent O(3), and four equivalent O(5) atoms to form distorted LaO12 cuboctahedra that share corners with two equivalent La(1)O12 cuboctahedra, faces with two equivalent La(1)O12 cuboctahedra, faces with two equivalent Mg(1)O6 octahedra, faces with two equivalent Mg(2)O6 octahedra, faces with two equivalent Mg(3)O6 octahedra, and faces with two equivalent Nb(1)O6 octahedra. In the second La site, La(2) is bonded in a 12-coordinate geometry to one O(1), two equivalent O(3), two equivalent O(5), three equivalent O(2), and four equivalent O(4) atoms. Nb(1) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form NbO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, and faces with two equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-12°. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(3), two equivalent La(1), and two equivalent La(2) atoms to form a mixture of distorted corner and face-sharing OLa4Mg2 octahedra. The corner-sharing octahedral tilt angles range from 0-54°. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Mg(2), one La(1), three equivalent La(2), and one Nb(1) atom. In the third O site, O(3) is bonded to one Mg(2), one Mg(3), two equivalent La(1), and two equivalent La(2) atoms to form a mixture of distorted edge, corner, and face-sharing OLa4Mg2 octahedra. The corner-sharing octahedral tilt angles range from 0-54°. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Mg(2), four equivalent La(2), and one Nb(1) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Mg(1), two equivalent La(1), two equivalent La(2), and one Nb(1) atom.
Mg2La3NbO9 crystallizes in the orthorhombic Immm space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mg(3)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with four equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-5°. Both Mg(1)-O(1) bond lengths are 2.00 Å. All Mg(1)-O(5) bond lengths are 2.03 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mg(3)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with two equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-12°. Both Mg(2)-O(2) bond lengths are 2.03 Å. Both Mg(2)-O(3) bond lengths are 2.03 Å. Both Mg(2)-O(4) bond lengths are 2.00 Å. In the third Mg site, Mg(3) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, and faces with four equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Mg(3)-O(1) bond lengths are 2.01 Å. All Mg(3)-O(3) bond lengths are 1.99 Å. There are two inequivalent La sites. In the first La site, La(1) is bonded to two equivalent O(1), two equivalent O(2), four equivalent O(3), and four equivalent O(5) atoms to form distorted LaO12 cuboctahedra that share corners with two equivalent La(1)O12 cuboctahedra, faces with two equivalent La(1)O12 cuboctahedra, faces with two equivalent Mg(1)O6 octahedra, faces with two equivalent Mg(2)O6 octahedra, faces with two equivalent Mg(3)O6 octahedra, and faces with two equivalent Nb(1)O6 octahedra. Both La(1)-O(1) bond lengths are 2.84 Å. Both La(1)-O(2) bond lengths are 2.67 Å. All La(1)-O(3) bond lengths are 2.67 Å. All La(1)-O(5) bond lengths are 3.08 Å. In the second La site, La(2) is bonded in a 12-coordinate geometry to one O(1), two equivalent O(3), two equivalent O(5), three equivalent O(2), and four equivalent O(4) atoms. The La(2)-O(1) bond length is 2.52 Å. Both La(2)-O(3) bond lengths are 2.60 Å. Both La(2)-O(5) bond lengths are 2.72 Å. There are two shorter (2.83 Å) and one longer (3.36 Å) La(2)-O(2) bond length. There are two shorter (2.85 Å) and two longer (3.17 Å) La(2)-O(4) bond lengths. Nb(1) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form NbO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, and faces with two equivalent La(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-12°. Both Nb(1)-O(2) bond lengths are 2.00 Å. Both Nb(1)-O(4) bond lengths are 1.98 Å. Both Nb(1)-O(5) bond lengths are 2.01 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(3), two equivalent La(1), and two equivalent La(2) atoms to form a mixture of distorted corner and face-sharing OLa4Mg2 octahedra. The corner-sharing octahedral tilt angles range from 0-54°. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Mg(2), one La(1), three equivalent La(2), and one Nb(1) atom. In the third O site, O(3) is bonded to one Mg(2), one Mg(3), two equivalent La(1), and two equivalent La(2) atoms to form a mixture of distorted edge, corner, and face-sharing OLa4Mg2 octahedra. The corner-sharing octahedral tilt angles range from 0-54°. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Mg(2), four equivalent La(2), and one Nb(1) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Mg(1), two equivalent La(1), two equivalent La(2), and one Nb(1) atom.