MgNi2(PO4)2 crystallizes in the monoclinic C2/c space group. Mg(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(8) atom. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(3), one O(4), one O(6), and one O(7) atom to form NiO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a cornercorner with one Ni(3)O4 trigonal pyramid. In the second Ni site, Ni(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(4) atoms. In the third Ni site, Ni(3) is bonded to two equivalent O(5) and two equivalent O(7) atoms to form NiO4 trigonal pyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent Ni(1)O5 trigonal bipyramids. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(4), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Ni(1)O5 trigonal bipyramids and  a cornercorner with one Ni(3)O4 trigonal pyramid. In the second P site, P(2) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O5 trigonal bipyramids and  a cornercorner with one Ni(3)O4 trigonal pyramid. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(2), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one P(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Ni(1), one Ni(2), and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Ni(3) and one P(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Mg(1), one Ni(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(3), and one P(1) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Mg(1) and one P(1) atom.
MgNi2(PO4)2 crystallizes in the monoclinic C2/c space group. Mg(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(8) atom. The Mg(1)-O(1) bond length is 2.13 Å. The Mg(1)-O(2) bond length is 2.11 Å. The Mg(1)-O(3) bond length is 2.32 Å. The Mg(1)-O(4) bond length is 2.47 Å. The Mg(1)-O(6) bond length is 2.18 Å. The Mg(1)-O(8) bond length is 2.01 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(3), one O(4), one O(6), and one O(7) atom to form NiO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a cornercorner with one Ni(3)O4 trigonal pyramid. The Ni(1)-O(2) bond length is 1.98 Å. The Ni(1)-O(3) bond length is 2.09 Å. The Ni(1)-O(4) bond length is 2.07 Å. The Ni(1)-O(6) bond length is 2.05 Å. The Ni(1)-O(7) bond length is 2.03 Å. In the second Ni site, Ni(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(4) atoms. Both Ni(2)-O(1) bond lengths are 2.02 Å. Both Ni(2)-O(4) bond lengths are 2.00 Å. In the third Ni site, Ni(3) is bonded to two equivalent O(5) and two equivalent O(7) atoms to form NiO4 trigonal pyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent Ni(1)O5 trigonal bipyramids. Both Ni(3)-O(5) bond lengths are 1.97 Å. Both Ni(3)-O(7) bond lengths are 1.99 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(4), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Ni(1)O5 trigonal bipyramids and  a cornercorner with one Ni(3)O4 trigonal pyramid. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(4) bond length is 1.59 Å. The P(1)-O(7) bond length is 1.56 Å. The P(1)-O(8) bond length is 1.51 Å. In the second P site, P(2) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O5 trigonal bipyramids and  a cornercorner with one Ni(3)O4 trigonal pyramid. The P(2)-O(2) bond length is 1.56 Å. The P(2)-O(3) bond length is 1.58 Å. The P(2)-O(5) bond length is 1.51 Å. The P(2)-O(6) bond length is 1.56 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(2), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one P(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Ni(1), one Ni(2), and one P(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Ni(3) and one P(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Mg(1), one Ni(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(3), and one P(1) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Mg(1) and one P(1) atom.