CaNiAs2O7 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(5), one O(6), two equivalent O(3), and two equivalent O(7) atoms. Ni(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form NiO5 square pyramids that share corners with two equivalent As(1)O4 tetrahedra and corners with three equivalent As(2)O4 tetrahedra. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form AsO4 tetrahedra that share corners with two equivalent Ni(1)O5 square pyramids and  a cornercorner with one As(2)O4 tetrahedra. In the second As site, As(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Ni(1)O5 square pyramids and  a cornercorner with one As(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ni(1), and one As(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ni(1), and one As(1) atom. In the third O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ni(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ni(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Ni(1), and one As(1) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one As(1) atom. In the seventh O site, O(4) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom.
CaNiAs2O7 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(5), one O(6), two equivalent O(3), and two equivalent O(7) atoms. The Ca(1)-O(1) bond length is 2.41 Å. The Ca(1)-O(2) bond length is 2.83 Å. The Ca(1)-O(5) bond length is 2.38 Å. The Ca(1)-O(6) bond length is 2.55 Å. There is one shorter (2.40 Å) and one longer (2.44 Å) Ca(1)-O(3) bond length. There is one shorter (2.42 Å) and one longer (2.87 Å) Ca(1)-O(7) bond length. Ni(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form NiO5 square pyramids that share corners with two equivalent As(1)O4 tetrahedra and corners with three equivalent As(2)O4 tetrahedra. The Ni(1)-O(1) bond length is 2.01 Å. The Ni(1)-O(2) bond length is 2.02 Å. The Ni(1)-O(5) bond length is 2.02 Å. The Ni(1)-O(6) bond length is 2.04 Å. The Ni(1)-O(7) bond length is 2.08 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form AsO4 tetrahedra that share corners with two equivalent Ni(1)O5 square pyramids and  a cornercorner with one As(2)O4 tetrahedra. The As(1)-O(2) bond length is 1.70 Å. The As(1)-O(3) bond length is 1.70 Å. The As(1)-O(4) bond length is 1.81 Å. The As(1)-O(6) bond length is 1.70 Å. In the second As site, As(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Ni(1)O5 square pyramids and  a cornercorner with one As(1)O4 tetrahedra. The As(2)-O(1) bond length is 1.70 Å. The As(2)-O(4) bond length is 1.78 Å. The As(2)-O(5) bond length is 1.70 Å. The As(2)-O(7) bond length is 1.71 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ni(1), and one As(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ni(1), and one As(1) atom. In the third O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ni(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ni(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Ni(1), and one As(1) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one As(1) atom. In the seventh O site, O(4) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom.