NiP2O7 crystallizes in the monoclinic C2 space group. Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 21-49°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Ni(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Ni(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ni(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent P(1) atoms.
NiP2O7 crystallizes in the monoclinic C2 space group. Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. Both Ni(1)-O(1) bond lengths are 2.04 Å. Both Ni(1)-O(2) bond lengths are 2.06 Å. Both Ni(1)-O(3) bond lengths are 2.07 Å. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 21-49°. The P(1)-O(1) bond length is 1.53 Å. The P(1)-O(2) bond length is 1.52 Å. The P(1)-O(3) bond length is 1.53 Å. The P(1)-O(4) bond length is 1.60 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Ni(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Ni(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ni(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent P(1) atoms.