MgNiP2O7 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a distorted pentagonal planar geometry to one O(1), one O(2), one O(3), one O(4), and one O(7) atom. Ni(1) is bonded to one O(1), one O(3), one O(4), one O(6), and one O(7) atom to form distorted NiO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra and corners with two equivalent Ni(1)O5 trigonal bipyramids. In the second P site, P(2) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra and corners with three equivalent Ni(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Ni(1), and one P(2) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Mg(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Ni(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(1), and one P(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Ni(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a T-shaped geometry to one Mg(1), one Ni(1), and one P(2) atom.
MgNiP2O7 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a distorted pentagonal planar geometry to one O(1), one O(2), one O(3), one O(4), and one O(7) atom. The Mg(1)-O(1) bond length is 2.03 Å. The Mg(1)-O(2) bond length is 1.96 Å. The Mg(1)-O(3) bond length is 2.19 Å. The Mg(1)-O(4) bond length is 1.97 Å. The Mg(1)-O(7) bond length is 2.06 Å. Ni(1) is bonded to one O(1), one O(3), one O(4), one O(6), and one O(7) atom to form distorted NiO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. The Ni(1)-O(1) bond length is 2.09 Å. The Ni(1)-O(3) bond length is 2.09 Å. The Ni(1)-O(4) bond length is 2.17 Å. The Ni(1)-O(6) bond length is 1.96 Å. The Ni(1)-O(7) bond length is 2.04 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one P(2)O4 tetrahedra and corners with two equivalent Ni(1)O5 trigonal bipyramids. The P(1)-O(2) bond length is 1.51 Å. The P(1)-O(4) bond length is 1.55 Å. The P(1)-O(5) bond length is 1.66 Å. The P(1)-O(6) bond length is 1.52 Å. In the second P site, P(2) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra and corners with three equivalent Ni(1)O5 trigonal bipyramids. The P(2)-O(1) bond length is 1.54 Å. The P(2)-O(3) bond length is 1.52 Å. The P(2)-O(5) bond length is 1.61 Å. The P(2)-O(7) bond length is 1.55 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Ni(1), and one P(2) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Mg(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Ni(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(1), and one P(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Ni(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a T-shaped geometry to one Mg(1), one Ni(1), and one P(2) atom.