CaNi3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(7) 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  an edgeedge with one Ni(2)O6 octahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form NiO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-61°. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Ni(2)O6 octahedra, 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 41-59°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Ni(1), and one P(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one P(2) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one P(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ni(2), and one P(2) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ni(1), one Ni(2), and one P(1) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ni(1), and one P(1) atom. In the seventh O site, O(4) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom.
CaNi3(P2O7)2 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. Both Ca(1)-O(1) bond lengths are 2.45 Å. Both Ca(1)-O(2) bond lengths are 2.59 Å. Both Ca(1)-O(3) bond lengths are 2.55 Å. Both Ca(1)-O(5) bond lengths are 2.69 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(7) 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  an edgeedge with one Ni(2)O6 octahedra. The Ni(1)-O(2) bond length is 2.17 Å. The Ni(1)-O(3) bond length is 2.14 Å. The Ni(1)-O(5) bond length is 2.11 Å. The Ni(1)-O(6) bond length is 2.06 Å. There is one shorter (2.07 Å) and one longer (2.08 Å) Ni(1)-O(7) bond length. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form NiO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. Both Ni(2)-O(1) bond lengths are 2.10 Å. Both Ni(2)-O(2) bond lengths are 2.13 Å. Both Ni(2)-O(6) bond lengths are 2.06 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-61°. 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 1.61 Å. The P(1)-O(5) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Ni(2)O6 octahedra, 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 41-59°. The P(2)-O(1) bond length is 1.53 Å. The P(2)-O(4) bond length is 1.60 Å. The P(2)-O(6) bond length is 1.53 Å. The P(2)-O(7) bond length is 1.54 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Ni(1), and one P(1) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one P(2) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one P(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ni(2), and one P(2) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ni(1), one Ni(2), and one P(1) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ni(1), and one P(1) atom. In the seventh O site, O(4) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom.