Ni3(PO4)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(5), one O(6), and two equivalent O(2) atoms to form distorted NiO5 square pyramids that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent Ni(2)O5 trigonal bipyramids,  an edgeedge with one Ni(1)O5 square pyramid, and  an edgeedge with one P(2)O4 tetrahedra. In the second Ni site, Ni(2) is bonded to one O(1), one O(3), one O(5), one O(6), and one O(7) atom to form distorted NiO5 trigonal bipyramids that share corners with three equivalent Ni(1)O5 square pyramids, corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a cornercorner with one Ni(3)O5 trigonal bipyramid. In the third Ni site, Ni(3) is bonded to one O(7), two equivalent O(4), and two equivalent O(8) atoms to form distorted NiO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  a cornercorner with one Ni(2)O5 trigonal bipyramid, and edges with two equivalent Ni(3)O5 trigonal bipyramids. 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 Ni(1)O5 square pyramids, corners with two equivalent Ni(2)O5 trigonal bipyramids, and corners with two equivalent Ni(3)O5 trigonal bipyramids. In the second P site, P(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with three equivalent Ni(2)O5 trigonal bipyramids, corners with three equivalent Ni(3)O5 trigonal bipyramids, and  an edgeedge with one Ni(1)O5 square pyramid. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one P(2) atom. In the second O site, O(8) is bonded in a distorted trigonal planar geometry to two equivalent Ni(3) and one P(2) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one P(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one P(1) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ni(2) and one P(1) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Ni(3) and one P(1) atom. In the seventh O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one P(2) atom. In the eighth O site, O(6) is bonded in a 3-coordinate geometry to one Ni(1), one Ni(2), and one P(2) atom.
Ni3(PO4)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(5), one O(6), and two equivalent O(2) atoms to form distorted NiO5 square pyramids that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent Ni(2)O5 trigonal bipyramids,  an edgeedge with one Ni(1)O5 square pyramid, and  an edgeedge with one P(2)O4 tetrahedra. The Ni(1)-O(1) bond length is 2.01 Å. The Ni(1)-O(5) bond length is 2.06 Å. The Ni(1)-O(6) bond length is 2.21 Å. There is one shorter (2.00 Å) and one longer (2.06 Å) Ni(1)-O(2) bond length. In the second Ni site, Ni(2) is bonded to one O(1), one O(3), one O(5), one O(6), and one O(7) atom to form distorted NiO5 trigonal bipyramids that share corners with three equivalent Ni(1)O5 square pyramids, corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a cornercorner with one Ni(3)O5 trigonal bipyramid. The Ni(2)-O(1) bond length is 2.29 Å. The Ni(2)-O(3) bond length is 1.99 Å. The Ni(2)-O(5) bond length is 1.93 Å. The Ni(2)-O(6) bond length is 1.93 Å. The Ni(2)-O(7) bond length is 2.20 Å. In the third Ni site, Ni(3) is bonded to one O(7), two equivalent O(4), and two equivalent O(8) atoms to form distorted NiO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  a cornercorner with one Ni(2)O5 trigonal bipyramid, and edges with two equivalent Ni(3)O5 trigonal bipyramids. The Ni(3)-O(7) bond length is 2.07 Å. There is one shorter (1.97 Å) and one longer (2.11 Å) Ni(3)-O(4) bond length. There is one shorter (2.04 Å) and one longer (2.18 Å) Ni(3)-O(8) bond length. 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 Ni(1)O5 square pyramids, corners with two equivalent Ni(2)O5 trigonal bipyramids, and corners with two equivalent Ni(3)O5 trigonal bipyramids. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(2) bond length is 1.56 Å. The P(1)-O(3) bond length is 1.53 Å. The P(1)-O(4) bond length is 1.56 Å. In the second P site, P(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with three equivalent Ni(2)O5 trigonal bipyramids, corners with three equivalent Ni(3)O5 trigonal bipyramids, and  an edgeedge with one Ni(1)O5 square pyramid. The P(2)-O(5) bond length is 1.55 Å. The P(2)-O(6) bond length is 1.55 Å. The P(2)-O(7) bond length is 1.56 Å. The P(2)-O(8) bond length is 1.54 Å. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one P(2) atom. In the second O site, O(8) is bonded in a distorted trigonal planar geometry to two equivalent Ni(3) and one P(2) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one P(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one P(1) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ni(2) and one P(1) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Ni(3) and one P(1) atom. In the seventh O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one P(2) atom. In the eighth O site, O(6) is bonded in a 3-coordinate geometry to one Ni(1), one Ni(2), and one P(2) atom.