MgCu2O4 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Cu(1) is bonded to one O(2), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing CuO6 octahedra. The corner-sharing octahedral tilt angles range from 0-56°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1) and three equivalent Cu(1) atoms to form distorted OMg2Cu3 trigonal bipyramids that share corners with four equivalent O(3)Mg2Cu4 octahedra, corners with five equivalent O(2)Mg2Cu2 tetrahedra, corners with two equivalent O(1)Mg2Cu3 trigonal bipyramids, edges with three equivalent O(3)Mg2Cu4 octahedra,  an edgeedge with one O(2)Mg2Cu2 tetrahedra, and edges with five equivalent O(1)Mg2Cu3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 8-44°. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Cu(1) atoms to form OMg2Cu2 tetrahedra that share corners with two equivalent O(2)Mg2Cu2 tetrahedra, corners with ten equivalent O(1)Mg2Cu3 trigonal bipyramids, edges with four equivalent O(3)Mg2Cu4 octahedra, and edges with two equivalent O(1)Mg2Cu3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Mg(1) and four equivalent Cu(1) atoms to form distorted OMg2Cu4 octahedra that share corners with two equivalent O(3)Mg2Cu4 octahedra, corners with eight equivalent O(1)Mg2Cu3 trigonal bipyramids, edges with two equivalent O(3)Mg2Cu4 octahedra, edges with four equivalent O(2)Mg2Cu2 tetrahedra, and edges with six equivalent O(1)Mg2Cu3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 48°.
MgCu2O4 crystallizes in the orthorhombic Cmcm space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Both Mg(1)-O(2) bond lengths are 2.05 Å. Both Mg(1)-O(3) bond lengths are 2.55 Å. All Mg(1)-O(1) bond lengths are 2.22 Å. Cu(1) is bonded to one O(2), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing CuO6 octahedra. The corner-sharing octahedral tilt angles range from 0-56°. The Cu(1)-O(2) bond length is 1.89 Å. Both Cu(1)-O(3) bond lengths are 2.06 Å. There is one shorter (1.92 Å) and two longer (2.09 Å) Cu(1)-O(1) bond lengths. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1) and three equivalent Cu(1) atoms to form distorted OMg2Cu3 trigonal bipyramids that share corners with four equivalent O(3)Mg2Cu4 octahedra, corners with five equivalent O(2)Mg2Cu2 tetrahedra, corners with two equivalent O(1)Mg2Cu3 trigonal bipyramids, edges with three equivalent O(3)Mg2Cu4 octahedra,  an edgeedge with one O(2)Mg2Cu2 tetrahedra, and edges with five equivalent O(1)Mg2Cu3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 8-44°. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Cu(1) atoms to form OMg2Cu2 tetrahedra that share corners with two equivalent O(2)Mg2Cu2 tetrahedra, corners with ten equivalent O(1)Mg2Cu3 trigonal bipyramids, edges with four equivalent O(3)Mg2Cu4 octahedra, and edges with two equivalent O(1)Mg2Cu3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Mg(1) and four equivalent Cu(1) atoms to form distorted OMg2Cu4 octahedra that share corners with two equivalent O(3)Mg2Cu4 octahedra, corners with eight equivalent O(1)Mg2Cu3 trigonal bipyramids, edges with two equivalent O(3)Mg2Cu4 octahedra, edges with four equivalent O(2)Mg2Cu2 tetrahedra, and edges with six equivalent O(1)Mg2Cu3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 48°.