MgMn4(NiO4)2 crystallizes in the cubic F-43m space group. Mg(1) is bonded to four equivalent Mn(1) and four equivalent O(1) atoms to form MgMn4O4 tetrahedra that share corners with four equivalent Ni(2)O4 tetrahedra. Mn(1) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent O(1), and three equivalent O(2) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a tetrahedral geometry to four equivalent O(2) atoms. In the second Ni site, Ni(2) is bonded to four equivalent O(1) atoms to form NiO4 tetrahedra that share corners with four equivalent Mg(1)Mn4O4 tetrahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Mg(1), three equivalent Mn(1), and one Ni(2) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Mn(1) and one Ni(1) atom.
MgMn4(NiO4)2 crystallizes in the cubic F-43m space group. Mg(1) is bonded to four equivalent Mn(1) and four equivalent O(1) atoms to form MgMn4O4 tetrahedra that share corners with four equivalent Ni(2)O4 tetrahedra. All Mg(1)-Mn(1) bond lengths are 2.24 Å. All Mg(1)-O(1) bond lengths are 1.92 Å. Mn(1) is bonded in a 7-coordinate geometry to one Mg(1), three equivalent O(1), and three equivalent O(2) atoms. All Mn(1)-O(1) bond lengths are 2.41 Å. All Mn(1)-O(2) bond lengths are 2.10 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a tetrahedral geometry to four equivalent O(2) atoms. All Ni(1)-O(2) bond lengths are 1.98 Å. In the second Ni site, Ni(2) is bonded to four equivalent O(1) atoms to form NiO4 tetrahedra that share corners with four equivalent Mg(1)Mn4O4 tetrahedra. All Ni(2)-O(1) bond lengths are 2.00 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Mg(1), three equivalent Mn(1), and one Ni(2) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Mn(1) and one Ni(1) atom.