MgNi2(PO4)2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(2) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form distorted NiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra and edges with two equivalent Ni(2)O6 octahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra and edges with two equivalent Ni(1)O6 octahedra. P(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and corners with three equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-59°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Ni(1), one Ni(2), and one P(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Ni(2) and one P(1) atom.
MgNi2(PO4)2 crystallizes in the monoclinic C2/m space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(2) atoms. Both Mg(1)-O(1) bond lengths are 2.25 Å. All Mg(1)-O(2) bond lengths are 2.11 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form distorted NiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra and edges with two equivalent Ni(2)O6 octahedra. Both Ni(1)-O(1) bond lengths are 1.94 Å. All Ni(1)-O(2) bond lengths are 2.28 Å. In the second Ni site, Ni(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra and edges with two equivalent Ni(1)O6 octahedra. Both Ni(2)-O(3) bond lengths are 1.99 Å. All Ni(2)-O(2) bond lengths are 2.21 Å. P(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and corners with three equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-59°. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(3) bond length is 1.49 Å. Both P(1)-O(2) bond lengths are 1.61 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Ni(1), one Ni(2), and one P(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Ni(2) and one P(1) atom.