Zn3Si4(NiO7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted NiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, and  an edgeedge with one Zn(2)O4 tetrahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Zn(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), and two equivalent O(7) atoms. In the second Zn site, Zn(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted ZnO4 tetrahedra that share corners with two equivalent Ni(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-60°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Zn(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 65-71°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Ni(2), one Zn(1), one Zn(2), and one Si(2) atom to form corner-sharing OZn2SiNi tetrahedra. In the second O site, O(2) is bonded in a trigonal planar geometry to one Ni(1), one Ni(2), and one Zn(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ni(1), one Zn(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ni(1), one Ni(2), one Zn(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Zn(1) and one Si(1) atom.
Zn3Si4(NiO7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted NiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, and  an edgeedge with one Zn(2)O4 tetrahedra. Both Ni(1)-O(2) bond lengths are 1.88 Å. Both Ni(1)-O(3) bond lengths are 1.95 Å. Both Ni(1)-O(4) bond lengths are 2.20 Å. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Zn(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Ni(1)O6 octahedra. Both Ni(2)-O(1) bond lengths are 2.19 Å. Both Ni(2)-O(2) bond lengths are 1.85 Å. Both Ni(2)-O(4) bond lengths are 1.97 Å. There are two inequivalent Zn sites. In the first Zn site, Zn(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), and two equivalent O(7) atoms. The Zn(1)-O(1) bond length is 2.14 Å. The Zn(1)-O(2) bond length is 2.01 Å. The Zn(1)-O(4) bond length is 2.45 Å. There is one shorter (2.02 Å) and one longer (2.14 Å) Zn(1)-O(7) bond length. In the second Zn site, Zn(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted ZnO4 tetrahedra that share corners with two equivalent Ni(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. Both Zn(2)-O(1) bond lengths are 2.06 Å. Both Zn(2)-O(3) bond lengths are 2.03 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-60°. The Si(1)-O(4) bond length is 1.63 Å. The Si(1)-O(5) bond length is 1.64 Å. The Si(1)-O(6) bond length is 1.63 Å. The Si(1)-O(7) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Zn(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 65-71°. The Si(2)-O(1) bond length is 1.67 Å. The Si(2)-O(3) bond length is 1.62 Å. The Si(2)-O(5) bond length is 1.64 Å. The Si(2)-O(6) bond length is 1.65 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Ni(2), one Zn(1), one Zn(2), and one Si(2) atom to form corner-sharing OZn2SiNi tetrahedra. In the second O site, O(2) is bonded in a trigonal planar geometry to one Ni(1), one Ni(2), and one Zn(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ni(1), one Zn(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ni(1), one Ni(2), one Zn(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Zn(1) and one Si(1) atom.