MgLa2Se4 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 La(1)Se6 octahedra, corners with four equivalent La(2)Se6 octahedra,  an edgeedge with one La(2)Se6 octahedra, and edges with two equivalent La(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 60-62°. There are two inequivalent La sites. In the first La site, La(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form LaSe6 octahedra that share corners with four equivalent La(2)Se6 octahedra, corners with two equivalent Mg(1)Se4 tetrahedra, edges with two equivalent La(1)Se6 octahedra, edges with two equivalent La(2)Se6 octahedra, and edges with two equivalent Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-57°. In the second La site, La(2) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form LaSe6 octahedra that share corners with four equivalent La(1)Se6 octahedra, corners with four equivalent La(2)Se6 octahedra, corners with four equivalent Mg(1)Se4 tetrahedra, edges with two equivalent La(1)Se6 octahedra, and  an edgeedge with one Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-57°. 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 La(1), and two equivalent La(2) atoms. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one La(2), and two equivalent La(1) atoms. In the third Se site, Se(3) is bonded to one Mg(1), one La(2), and two equivalent La(1) atoms to form distorted corner-sharing SeLa3Mg tetrahedra.
MgLa2Se4 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 La(1)Se6 octahedra, corners with four equivalent La(2)Se6 octahedra,  an edgeedge with one La(2)Se6 octahedra, and edges with two equivalent La(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 60-62°. The Mg(1)-Se(2) bond length is 2.62 Å. The Mg(1)-Se(3) bond length is 2.55 Å. Both Mg(1)-Se(1) bond lengths are 2.60 Å. There are two inequivalent La sites. In the first La site, La(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form LaSe6 octahedra that share corners with four equivalent La(2)Se6 octahedra, corners with two equivalent Mg(1)Se4 tetrahedra, edges with two equivalent La(1)Se6 octahedra, edges with two equivalent La(2)Se6 octahedra, and edges with two equivalent Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-57°. Both La(1)-Se(1) bond lengths are 3.05 Å. Both La(1)-Se(2) bond lengths are 3.00 Å. Both La(1)-Se(3) bond lengths are 3.00 Å. In the second La site, La(2) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form LaSe6 octahedra that share corners with four equivalent La(1)Se6 octahedra, corners with four equivalent La(2)Se6 octahedra, corners with four equivalent Mg(1)Se4 tetrahedra, edges with two equivalent La(1)Se6 octahedra, and  an edgeedge with one Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-57°. The La(2)-Se(2) bond length is 2.98 Å. The La(2)-Se(3) bond length is 3.01 Å. There are two shorter (3.06 Å) and two longer (3.07 Å) La(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 La(1), and two equivalent La(2) atoms. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one La(2), and two equivalent La(1) atoms. In the third Se site, Se(3) is bonded to one Mg(1), one La(2), and two equivalent La(1) atoms to form distorted corner-sharing SeLa3Mg tetrahedra.