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(5), and two equivalent O(7) atoms to form distorted LiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Li(1)O6 octahedra, and edges with two equivalent Ni(1)O5 trigonal bipyramids. Ni(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form NiO5 trigonal bipyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and edges with two equivalent Li(1)O6 octahedra. There are two inequivalent P sites. In the first P site, 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 Li(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with three equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 42-54°. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Li(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with two equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 45-54°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(1) 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 bent 150 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ni(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Li(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(5), and two equivalent O(7) atoms to form distorted LiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Li(1)O6 octahedra, and edges with two equivalent Ni(1)O5 trigonal bipyramids. The Li(1)-O(1) bond length is 2.37 Å. The Li(1)-O(2) bond length is 2.29 Å. The Li(1)-O(3) bond length is 2.15 Å. The Li(1)-O(5) bond length is 2.12 Å. There is one shorter (2.04 Å) and one longer (2.24 Å) Li(1)-O(7) bond length. Ni(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form NiO5 trigonal bipyramids that share corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(1)O4 tetrahedra, and edges with two equivalent Li(1)O6 octahedra. The Ni(1)-O(1) bond length is 1.98 Å. The Ni(1)-O(2) bond length is 2.04 Å. The Ni(1)-O(3) bond length is 2.01 Å. The Ni(1)-O(5) bond length is 2.01 Å. The Ni(1)-O(6) bond length is 2.01 Å. There are two inequivalent P sites. In the first P site, 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 Li(1)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with three equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 42-54°. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.54 Å. The P(1)-O(3) bond length is 1.53 Å. The P(1)-O(4) bond length is 1.60 Å. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Li(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with two equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 45-54°. The P(2)-O(4) bond length is 1.61 Å. The P(2)-O(5) bond length is 1.53 Å. The P(2)-O(6) bond length is 1.53 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 distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(1) 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 bent 150 degrees geometry to one P(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Li(1), one Ni(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ni(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Li(1) and one P(2) atom.