MgCu2(SeO4)2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(3) and four equivalent O(2) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form distorted CuO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra and edges with two equivalent Cu(2)O6 octahedra. In the second Cu site, Cu(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form CuO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra and edges with two equivalent Cu(1)O6 octahedra. Se(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form distorted SeO4 tetrahedra that share corners with three equivalent Cu(1)O6 octahedra and corners with three equivalent Cu(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-64°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Cu(2) and one Se(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Cu(1), one Cu(2), and one Se(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one Se(1) atom.
MgCu2(SeO4)2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(3) and four equivalent O(2) atoms. Both Mg(1)-O(3) bond lengths are 2.53 Å. All Mg(1)-O(2) bond lengths are 2.15 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form distorted CuO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra and edges with two equivalent Cu(2)O6 octahedra. Both Cu(1)-O(3) bond lengths are 1.91 Å. All Cu(1)-O(2) bond lengths are 2.42 Å. In the second Cu site, Cu(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form CuO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra and edges with two equivalent Cu(1)O6 octahedra. Both Cu(2)-O(1) bond lengths are 1.93 Å. All Cu(2)-O(2) bond lengths are 2.41 Å. Se(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form distorted SeO4 tetrahedra that share corners with three equivalent Cu(1)O6 octahedra and corners with three equivalent Cu(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-64°. The Se(1)-O(1) bond length is 1.68 Å. The Se(1)-O(3) bond length is 1.72 Å. Both Se(1)-O(2) bond lengths are 1.76 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Cu(2) and one Se(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Cu(1), one Cu(2), and one Se(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one Se(1) atom.