NiZnAs2O7 crystallizes in the monoclinic P2_1/c space group. 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 trigonal bipyramids that share corners with two equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with two equivalent Zn(1)O6 octahedra. Zn(1) is bonded to one O(1), one O(5), one O(6), one O(7), and two equivalent O(3) atoms to form distorted ZnO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Zn(1)O6 octahedra, and edges with two equivalent Ni(1)O5 trigonal bipyramids. 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 three equivalent Zn(1)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, and corners with two equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 53-54°. 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 Zn(1)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, and corners with three equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 39-56°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(1), one Zn(1), and one As(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(1), one Zn(1), and one As(1) atom. In the third O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Ni(1), one Zn(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Ni(1), one Zn(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Ni(1) and one As(1) atom. In the sixth O site, O(3) is bonded in a trigonal planar geometry to two equivalent Zn(1) and one As(1) atom. In the seventh O site, O(4) is bonded in a bent 150 degrees geometry to one As(1) and one As(2) atom.
NiZnAs2O7 crystallizes in the monoclinic P2_1/c space group. 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 trigonal bipyramids that share corners with two equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with two equivalent Zn(1)O6 octahedra. The Ni(1)-O(1) bond length is 2.03 Å. The Ni(1)-O(2) bond length is 1.95 Å. The Ni(1)-O(5) bond length is 1.99 Å. The Ni(1)-O(6) bond length is 2.03 Å. The Ni(1)-O(7) bond length is 2.03 Å. Zn(1) is bonded to one O(1), one O(5), one O(6), one O(7), and two equivalent O(3) atoms to form distorted ZnO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Zn(1)O6 octahedra, and edges with two equivalent Ni(1)O5 trigonal bipyramids. The Zn(1)-O(1) bond length is 2.10 Å. The Zn(1)-O(5) bond length is 2.17 Å. The Zn(1)-O(6) bond length is 2.10 Å. The Zn(1)-O(7) bond length is 2.12 Å. There is one shorter (2.03 Å) and one longer (2.15 Å) Zn(1)-O(3) bond length. 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 three equivalent Zn(1)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, and corners with two equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 53-54°. The As(1)-O(2) bond length is 1.66 Å. The As(1)-O(3) bond length is 1.69 Å. The As(1)-O(4) bond length is 1.75 Å. The As(1)-O(6) bond length is 1.69 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 Zn(1)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, and corners with three equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 39-56°. The As(2)-O(1) bond length is 1.69 Å. The As(2)-O(4) bond length is 1.74 Å. The As(2)-O(5) bond length is 1.69 Å. The As(2)-O(7) bond length is 1.69 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(1), one Zn(1), and one As(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(1), one Zn(1), and one As(1) atom. In the third O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Ni(1), one Zn(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Ni(1), one Zn(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Ni(1) and one As(1) atom. In the sixth O site, O(3) is bonded in a trigonal planar geometry to two equivalent Zn(1) and one As(1) atom. In the seventh O site, O(4) is bonded in a bent 150 degrees geometry to one As(1) and one As(2) atom.