LiNiP2O7 crystallizes in the monoclinic P2_1/c space group. Li(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form LiO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. Ni(1) is bonded to one O(2), one O(3), one O(4), one O(7), and two equivalent O(5) atoms to form NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, and edges with two equivalent Li(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(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 46-54°. In the second P site, P(2) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with three equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 30-50°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Li(1) and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Li(1), one Ni(1), and one P(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom.
LiNiP2O7 crystallizes in the monoclinic P2_1/c space group. Li(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form LiO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. The Li(1)-O(1) bond length is 1.99 Å. The Li(1)-O(2) bond length is 2.18 Å. The Li(1)-O(3) bond length is 2.09 Å. The Li(1)-O(4) bond length is 2.06 Å. The Li(1)-O(7) bond length is 2.11 Å. Ni(1) is bonded to one O(2), one O(3), one O(4), one O(7), and two equivalent O(5) atoms to form NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, and edges with two equivalent Li(1)O5 trigonal bipyramids. The Ni(1)-O(2) bond length is 2.11 Å. The Ni(1)-O(3) bond length is 2.04 Å. The Ni(1)-O(4) bond length is 2.11 Å. The Ni(1)-O(7) bond length is 2.04 Å. There is one shorter (2.09 Å) and one longer (2.22 Å) Ni(1)-O(5) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 46-54°. The P(1)-O(1) bond length is 1.52 Å. The P(1)-O(3) bond length is 1.51 Å. The P(1)-O(5) bond length is 1.56 Å. The P(1)-O(6) bond length is 1.61 Å. In the second P site, P(2) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with three equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 30-50°. The P(2)-O(2) bond length is 1.54 Å. The P(2)-O(4) bond length is 1.54 Å. The P(2)-O(6) bond length is 1.61 Å. The P(2)-O(7) bond length is 1.52 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Li(1) and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Li(1), one Ni(1), and one P(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom.