MgCr2(NiO4)2 crystallizes in the orthorhombic Amm2 space group. Mg(1) is bonded to two equivalent O(1) and two equivalent O(4) atoms to form distorted MgO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra, corners with two equivalent Cr(1)O4 tetrahedra, and  an edgeedge with one Cr(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 66-68°. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form CrO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-52°. In the second Cr site, Cr(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form CrO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-58°. Ni(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form NiO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Cr(2), and two equivalent Ni(1) atoms to form distorted edge-sharing OMgCrNi2 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Cr(2) and one Ni(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Cr(1), and one Ni(1) atom.
MgCr2(NiO4)2 crystallizes in the orthorhombic Amm2 space group. Mg(1) is bonded to two equivalent O(1) and two equivalent O(4) atoms to form distorted MgO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra, corners with two equivalent Cr(1)O4 tetrahedra, and  an edgeedge with one Cr(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 66-68°. Both Mg(1)-O(1) bond lengths are 2.04 Å. Both Mg(1)-O(4) bond lengths are 1.96 Å. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form CrO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-52°. Both Cr(1)-O(2) bond lengths are 1.72 Å. Both Cr(1)-O(4) bond lengths are 1.75 Å. In the second Cr site, Cr(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form CrO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-58°. Both Cr(2)-O(1) bond lengths are 1.85 Å. Both Cr(2)-O(3) bond lengths are 1.65 Å. Ni(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form NiO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. The Ni(1)-O(3) bond length is 2.05 Å. The Ni(1)-O(4) bond length is 2.05 Å. Both Ni(1)-O(1) bond lengths are 2.17 Å. Both Ni(1)-O(2) bond lengths are 2.09 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Cr(2), and two equivalent Ni(1) atoms to form distorted edge-sharing OMgCrNi2 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cr(1) and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Cr(2) and one Ni(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Cr(1), and one Ni(1) atom.