Mg(InSe2)2 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form MgSe4 tetrahedra that share corners with two equivalent In(1)Se6 octahedra, corners with four equivalent In(2)Se6 octahedra,  an edgeedge with one In(2)Se6 octahedra, and edges with two equivalent In(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 62-67°. There are two inequivalent In sites. In the first In site, In(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form InSe6 octahedra that share corners with four equivalent In(2)Se6 octahedra, corners with two equivalent Mg(1)Se4 tetrahedra, edges with two equivalent In(1)Se6 octahedra, edges with two equivalent In(2)Se6 octahedra, and edges with two equivalent Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-53°. In the second In site, In(2) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form InSe6 octahedra that share corners with four equivalent In(1)Se6 octahedra, corners with four equivalent In(2)Se6 octahedra, corners with four equivalent Mg(1)Se4 tetrahedra, edges with two equivalent In(1)Se6 octahedra, and  an edgeedge with one Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-53°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one In(1), and two equivalent In(2) atoms. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one In(2), and two equivalent In(1) atoms. In the third Se site, Se(3) is bonded to one Mg(1), one In(2), and two equivalent In(1) atoms to form distorted corner-sharing SeMgIn3 tetrahedra.
Mg(InSe2)2 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form MgSe4 tetrahedra that share corners with two equivalent In(1)Se6 octahedra, corners with four equivalent In(2)Se6 octahedra,  an edgeedge with one In(2)Se6 octahedra, and edges with two equivalent In(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 62-67°. The Mg(1)-Se(2) bond length is 2.60 Å. The Mg(1)-Se(3) bond length is 2.56 Å. Both Mg(1)-Se(1) bond lengths are 2.59 Å. There are two inequivalent In sites. In the first In site, In(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form InSe6 octahedra that share corners with four equivalent In(2)Se6 octahedra, corners with two equivalent Mg(1)Se4 tetrahedra, edges with two equivalent In(1)Se6 octahedra, edges with two equivalent In(2)Se6 octahedra, and edges with two equivalent Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-53°. Both In(1)-Se(1) bond lengths are 2.83 Å. Both In(1)-Se(2) bond lengths are 2.85 Å. Both In(1)-Se(3) bond lengths are 2.74 Å. In the second In site, In(2) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form InSe6 octahedra that share corners with four equivalent In(1)Se6 octahedra, corners with four equivalent In(2)Se6 octahedra, corners with four equivalent Mg(1)Se4 tetrahedra, edges with two equivalent In(1)Se6 octahedra, and  an edgeedge with one Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-53°. The In(2)-Se(2) bond length is 2.72 Å. The In(2)-Se(3) bond length is 2.77 Å. There are two shorter (2.83 Å) and two longer (2.98 Å) In(2)-Se(1) bond lengths. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one In(1), and two equivalent In(2) atoms. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one In(2), and two equivalent In(1) atoms. In the third Se site, Se(3) is bonded to one Mg(1), one In(2), and two equivalent In(1) atoms to form distorted corner-sharing SeMgIn3 tetrahedra.