MgTi2Nb2(CuO4)3 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(4), four equivalent O(2), and four equivalent O(3) atoms to form MgO12 cuboctahedra that share faces with four equivalent Ti(1)O6 octahedra and faces with four equivalent Nb(1)O6 octahedra. Ti(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with two equivalent Mg(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 37-38°. Nb(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Ti(1)O6 octahedra, and faces with two equivalent Mg(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 38-39°. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to four equivalent O(3) atoms. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to four equivalent O(2) atoms. In the third Cu site, Cu(3) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Ti(1), and one Cu(3) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Nb(1), and one Cu(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Nb(1), and one Cu(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Nb(1), and one Cu(3) atom.
MgTi2Nb2(CuO4)3 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(4), four equivalent O(2), and four equivalent O(3) atoms to form MgO12 cuboctahedra that share faces with four equivalent Ti(1)O6 octahedra and faces with four equivalent Nb(1)O6 octahedra. Both Mg(1)-O(1) bond lengths are 2.62 Å. Both Mg(1)-O(4) bond lengths are 2.62 Å. All Mg(1)-O(2) bond lengths are 2.62 Å. All Mg(1)-O(3) bond lengths are 2.63 Å. Ti(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TiO6 octahedra that share corners with two equivalent Ti(1)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with two equivalent Mg(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 37-38°. Both Ti(1)-O(1) bond lengths are 2.00 Å. Both Ti(1)-O(2) bond lengths are 1.99 Å. Both Ti(1)-O(3) bond lengths are 1.99 Å. Nb(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Ti(1)O6 octahedra, and faces with two equivalent Mg(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 38-39°. Both Nb(1)-O(2) bond lengths are 2.01 Å. Both Nb(1)-O(3) bond lengths are 2.02 Å. Both Nb(1)-O(4) bond lengths are 2.01 Å. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to four equivalent O(3) atoms. All Cu(1)-O(3) bond lengths are 2.04 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to four equivalent O(2) atoms. All Cu(2)-O(2) bond lengths are 2.04 Å. In the third Cu site, Cu(3) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(4) atoms. Both Cu(3)-O(1) bond lengths are 2.06 Å. Both Cu(3)-O(4) bond lengths are 2.01 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Ti(1), and one Cu(3) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Nb(1), and one Cu(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Nb(1), and one Cu(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Nb(1), and one Cu(3) atom.