MgEu2S4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form MgS4 tetrahedra that share corners with two equivalent Eu(1)S6 octahedra, corners with four equivalent Eu(2)S6 octahedra,  an edgeedge with one Eu(2)S6 octahedra, and edges with two equivalent Eu(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 59-65°. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form EuS6 octahedra that share corners with four equivalent Eu(2)S6 octahedra, corners with two equivalent Mg(1)S4 tetrahedra, edges with two equivalent Eu(1)S6 octahedra, edges with two equivalent Eu(2)S6 octahedra, and edges with two equivalent Mg(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-56°. In the second Eu site, Eu(2) is bonded to one S(2), one S(3), and four equivalent S(1) atoms to form EuS6 octahedra that share corners with four equivalent Eu(1)S6 octahedra, corners with four equivalent Eu(2)S6 octahedra, corners with four equivalent Mg(1)S4 tetrahedra, edges with two equivalent Eu(1)S6 octahedra, and  an edgeedge with one Mg(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-56°. There are three inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Eu(1), and two equivalent Eu(2) atoms. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Eu(2), and two equivalent Eu(1) atoms. In the third S site, S(3) is bonded to one Mg(1), one Eu(2), and two equivalent Eu(1) atoms to form distorted corner-sharing SEu3Mg trigonal pyramids.
MgEu2S4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form MgS4 tetrahedra that share corners with two equivalent Eu(1)S6 octahedra, corners with four equivalent Eu(2)S6 octahedra,  an edgeedge with one Eu(2)S6 octahedra, and edges with two equivalent Eu(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 59-65°. The Mg(1)-S(2) bond length is 2.49 Å. The Mg(1)-S(3) bond length is 2.40 Å. Both Mg(1)-S(1) bond lengths are 2.47 Å. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form EuS6 octahedra that share corners with four equivalent Eu(2)S6 octahedra, corners with two equivalent Mg(1)S4 tetrahedra, edges with two equivalent Eu(1)S6 octahedra, edges with two equivalent Eu(2)S6 octahedra, and edges with two equivalent Mg(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-56°. Both Eu(1)-S(1) bond lengths are 2.86 Å. Both Eu(1)-S(2) bond lengths are 2.81 Å. Both Eu(1)-S(3) bond lengths are 2.79 Å. In the second Eu site, Eu(2) is bonded to one S(2), one S(3), and four equivalent S(1) atoms to form EuS6 octahedra that share corners with four equivalent Eu(1)S6 octahedra, corners with four equivalent Eu(2)S6 octahedra, corners with four equivalent Mg(1)S4 tetrahedra, edges with two equivalent Eu(1)S6 octahedra, and  an edgeedge with one Mg(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-56°. The Eu(2)-S(2) bond length is 2.81 Å. The Eu(2)-S(3) bond length is 2.85 Å. All Eu(2)-S(1) bond lengths are 2.89 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Eu(1), and two equivalent Eu(2) atoms. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Eu(2), and two equivalent Eu(1) atoms. In the third S site, S(3) is bonded to one Mg(1), one Eu(2), and two equivalent Eu(1) atoms to form distorted corner-sharing SEu3Mg trigonal pyramids.