MgFe2(NiO3)2 crystallizes in the trigonal R-3 space group. Mg(1) is bonded to six equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent Fe(1)O6 octahedra, edges with six equivalent Ni(1)O6 octahedra, and faces with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 41°. Fe(1) is bonded to six equivalent O(1) atoms to form FeO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with nine equivalent Ni(1)O6 octahedra, edges with three equivalent Fe(1)O6 octahedra,  a faceface with one Mg(1)O6 octahedra, and  a faceface with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-56°. Ni(1) is bonded to six equivalent O(1) atoms to form distorted NiO6 octahedra that share corners with nine equivalent Fe(1)O6 octahedra, edges with three equivalent Mg(1)O6 octahedra, edges with three equivalent Ni(1)O6 octahedra, and  a faceface with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-56°. O(1) is bonded to one Mg(1), two equivalent Fe(1), and two equivalent Ni(1) atoms to form a mixture of distorted corner and edge-sharing OMgFe2Ni2 trigonal bipyramids.
MgFe2(NiO3)2 crystallizes in the trigonal R-3 space group. Mg(1) is bonded to six equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent Fe(1)O6 octahedra, edges with six equivalent Ni(1)O6 octahedra, and faces with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 41°. All Mg(1)-O(1) bond lengths are 2.05 Å. Fe(1) is bonded to six equivalent O(1) atoms to form FeO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with nine equivalent Ni(1)O6 octahedra, edges with three equivalent Fe(1)O6 octahedra,  a faceface with one Mg(1)O6 octahedra, and  a faceface with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-56°. There are three shorter (1.99 Å) and three longer (2.15 Å) Fe(1)-O(1) bond lengths. Ni(1) is bonded to six equivalent O(1) atoms to form distorted NiO6 octahedra that share corners with nine equivalent Fe(1)O6 octahedra, edges with three equivalent Mg(1)O6 octahedra, edges with three equivalent Ni(1)O6 octahedra, and  a faceface with one Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-56°. There are three shorter (2.04 Å) and three longer (2.31 Å) Ni(1)-O(1) bond lengths. O(1) is bonded to one Mg(1), two equivalent Fe(1), and two equivalent Ni(1) atoms to form a mixture of distorted corner and edge-sharing OMgFe2Ni2 trigonal bipyramids.