MgSm2Cr2O8 is Esseneite-like structured and crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent Cr(1)O4 tetrahedra and edges with two equivalent Cr(1)O4 tetrahedra. Sm(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Cr(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Sm(1), and one Cr(1) atom. In the second O site, O(2) is bonded to one Mg(1), two equivalent Sm(1), and one Cr(1) atom to form distorted corner-sharing OSm2MgCr trigonal pyramids. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Sm(1) and one Cr(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Sm(1), and one Cr(1) atom.
MgSm2Cr2O8 is Esseneite-like structured and crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent Cr(1)O4 tetrahedra and edges with two equivalent Cr(1)O4 tetrahedra. Both Mg(1)-O(1) bond lengths are 2.34 Å. Both Mg(1)-O(2) bond lengths are 1.99 Å. Both Mg(1)-O(4) bond lengths are 2.11 Å. Sm(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There is one shorter (2.39 Å) and one longer (2.54 Å) Sm(1)-O(1) bond length. There is one shorter (2.44 Å) and one longer (2.53 Å) Sm(1)-O(2) bond length. There is one shorter (2.31 Å) and one longer (2.43 Å) Sm(1)-O(3) bond length. There is one shorter (2.47 Å) and one longer (2.71 Å) Sm(1)-O(4) bond length. Cr(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. The Cr(1)-O(1) bond length is 1.83 Å. The Cr(1)-O(2) bond length is 1.86 Å. The Cr(1)-O(3) bond length is 1.76 Å. The Cr(1)-O(4) bond length is 1.77 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Sm(1), and one Cr(1) atom. In the second O site, O(2) is bonded to one Mg(1), two equivalent Sm(1), and one Cr(1) atom to form distorted corner-sharing OSm2MgCr trigonal pyramids. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Sm(1) and one Cr(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), two equivalent Sm(1), and one Cr(1) atom.