MgCu3AlSe4 crystallizes in the cubic P-43m space group. Mg(1) is bonded to four equivalent Se(1) atoms to form MgSe4 tetrahedra that share corners with four equivalent Al(1)Se4 tetrahedra and corners with twelve equivalent Cu(1)Se4 tetrahedra. Cu(1) is bonded to four equivalent Se(1) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Mg(1)Se4 tetrahedra, corners with eight equivalent Cu(1)Se4 tetrahedra, and edges with two equivalent Al(1)Se4 tetrahedra. Al(1) is bonded to four equivalent Se(1) atoms to form AlSe4 tetrahedra that share corners with four equivalent Mg(1)Se4 tetrahedra and edges with six equivalent Cu(1)Se4 tetrahedra. Se(1) is bonded in a distorted pentagonal planar geometry to one Mg(1), three equivalent Cu(1), and one Al(1) atom.
MgCu3AlSe4 crystallizes in the cubic P-43m space group. Mg(1) is bonded to four equivalent Se(1) atoms to form MgSe4 tetrahedra that share corners with four equivalent Al(1)Se4 tetrahedra and corners with twelve equivalent Cu(1)Se4 tetrahedra. All Mg(1)-Se(1) bond lengths are 2.59 Å. Cu(1) is bonded to four equivalent Se(1) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Mg(1)Se4 tetrahedra, corners with eight equivalent Cu(1)Se4 tetrahedra, and edges with two equivalent Al(1)Se4 tetrahedra. All Cu(1)-Se(1) bond lengths are 2.48 Å. Al(1) is bonded to four equivalent Se(1) atoms to form AlSe4 tetrahedra that share corners with four equivalent Mg(1)Se4 tetrahedra and edges with six equivalent Cu(1)Se4 tetrahedra. All Al(1)-Se(1) bond lengths are 2.42 Å. Se(1) is bonded in a distorted pentagonal planar geometry to one Mg(1), three equivalent Cu(1), and one Al(1) atom.