MgPr2Se4 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 Pr(1)Se6 octahedra, corners with four equivalent Pr(2)Se6 octahedra,  an edgeedge with one Pr(2)Se6 octahedra, and edges with two equivalent Pr(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 59-63°. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form PrSe6 octahedra that share corners with four equivalent Pr(2)Se6 octahedra, corners with two equivalent Mg(1)Se4 tetrahedra, edges with two equivalent Pr(1)Se6 octahedra, edges with two equivalent Pr(2)Se6 octahedra, and edges with two equivalent Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-56°. In the second Pr site, Pr(2) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form PrSe6 octahedra that share corners with four equivalent Pr(1)Se6 octahedra, corners with four equivalent Pr(2)Se6 octahedra, corners with four equivalent Mg(1)Se4 tetrahedra, edges with two equivalent Pr(1)Se6 octahedra, and  an edgeedge with one Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-56°. 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 Pr(1), and two equivalent Pr(2) atoms. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Pr(2), and two equivalent Pr(1) atoms. In the third Se site, Se(3) is bonded to one Mg(1), one Pr(2), and two equivalent Pr(1) atoms to form distorted corner-sharing SePr3Mg trigonal pyramids.
MgPr2Se4 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 Pr(1)Se6 octahedra, corners with four equivalent Pr(2)Se6 octahedra,  an edgeedge with one Pr(2)Se6 octahedra, and edges with two equivalent Pr(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 59-63°. The Mg(1)-Se(2) bond length is 2.62 Å. The Mg(1)-Se(3) bond length is 2.54 Å. Both Mg(1)-Se(1) bond lengths are 2.60 Å. There are two inequivalent Pr sites. In the first Pr site, Pr(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form PrSe6 octahedra that share corners with four equivalent Pr(2)Se6 octahedra, corners with two equivalent Mg(1)Se4 tetrahedra, edges with two equivalent Pr(1)Se6 octahedra, edges with two equivalent Pr(2)Se6 octahedra, and edges with two equivalent Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-56°. Both Pr(1)-Se(1) bond lengths are 3.03 Å. Both Pr(1)-Se(2) bond lengths are 2.98 Å. Both Pr(1)-Se(3) bond lengths are 2.97 Å. In the second Pr site, Pr(2) is bonded to one Se(2), one Se(3), and four equivalent Se(1) atoms to form PrSe6 octahedra that share corners with four equivalent Pr(1)Se6 octahedra, corners with four equivalent Pr(2)Se6 octahedra, corners with four equivalent Mg(1)Se4 tetrahedra, edges with two equivalent Pr(1)Se6 octahedra, and  an edgeedge with one Mg(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-56°. The Pr(2)-Se(2) bond length is 2.96 Å. The Pr(2)-Se(3) bond length is 2.99 Å. All Pr(2)-Se(1) bond lengths are 3.04 Å. 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 Pr(1), and two equivalent Pr(2) atoms. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Pr(2), and two equivalent Pr(1) atoms. In the third Se site, Se(3) is bonded to one Mg(1), one Pr(2), and two equivalent Pr(1) atoms to form distorted corner-sharing SePr3Mg trigonal pyramids.