Na6Ni(SO4)4 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(6), one O(8), two equivalent O(3), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded to one O(2), one O(4), one O(7), one O(8), and two equivalent O(6) atoms to form NaO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent S(1)O4 tetrahedra, corners with two equivalent S(2)O4 tetrahedra,  an edgeedge with one Na(2)O6 octahedra, and  an edgeedge with one S(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. In the third Na site, Na(3) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(5), one O(7), one O(8), and two equivalent O(2) atoms. Ni(1) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(7) atoms to form NiO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with two equivalent S(2)O4 tetrahedra, and corners with four equivalent S(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form SO4 tetrahedra that share corners with two equivalent Na(2)O6 octahedra and corners with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 15-63°. In the second S site, S(2) is bonded to one O(3), one O(6), one O(7), and one O(8) atom to form SO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Na(2)O6 octahedra, and  an edgeedge with one Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-46°. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(1), and one S(1) atom. In the second O site, O(5) is bonded in a 3-coordinate geometry to one Na(3), one Ni(1), and one S(1) atom. In the third O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one S(2) atom. In the fourth O site, O(7) is bonded in a 4-coordinate geometry to one Na(2), one Na(3), one Ni(1), and one S(2) atom. In the fifth O site, O(8) is bonded to one Na(1), one Na(2), one Na(3), and one S(2) atom to form a mixture of distorted edge and corner-sharing ONa3S tetrahedra. In the sixth O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(3), one Ni(1), and one S(1) atom. In the seventh O site, O(2) is bonded to one Na(2), two equivalent Na(3), and one S(1) atom to form a mixture of distorted edge and corner-sharing ONa3S tetrahedra. In the eighth O site, O(3) is bonded in a 4-coordinate geometry to one Na(3), two equivalent Na(1), and one S(2) atom.
Na6Ni(SO4)4 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(6), one O(8), two equivalent O(3), and two equivalent O(4) atoms. The Na(1)-O(6) bond length is 2.40 Å. The Na(1)-O(8) bond length is 2.42 Å. There is one shorter (2.35 Å) and one longer (2.42 Å) Na(1)-O(3) bond length. There is one shorter (2.38 Å) and one longer (2.72 Å) Na(1)-O(4) bond length. In the second Na site, Na(2) is bonded to one O(2), one O(4), one O(7), one O(8), and two equivalent O(6) atoms to form NaO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent S(1)O4 tetrahedra, corners with two equivalent S(2)O4 tetrahedra,  an edgeedge with one Na(2)O6 octahedra, and  an edgeedge with one S(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. The Na(2)-O(2) bond length is 2.33 Å. The Na(2)-O(4) bond length is 2.37 Å. The Na(2)-O(7) bond length is 2.40 Å. The Na(2)-O(8) bond length is 2.29 Å. There is one shorter (2.30 Å) and one longer (2.45 Å) Na(2)-O(6) bond length. In the third Na site, Na(3) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(5), one O(7), one O(8), and two equivalent O(2) atoms. The Na(3)-O(1) bond length is 2.25 Å. The Na(3)-O(3) bond length is 2.65 Å. The Na(3)-O(5) bond length is 2.55 Å. The Na(3)-O(7) bond length is 2.62 Å. The Na(3)-O(8) bond length is 2.32 Å. There is one shorter (2.41 Å) and one longer (2.46 Å) Na(3)-O(2) bond length. Ni(1) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(7) atoms to form NiO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with two equivalent S(2)O4 tetrahedra, and corners with four equivalent S(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. Both Ni(1)-O(1) bond lengths are 2.04 Å. Both Ni(1)-O(5) bond lengths are 2.11 Å. Both Ni(1)-O(7) bond lengths are 2.04 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form SO4 tetrahedra that share corners with two equivalent Na(2)O6 octahedra and corners with two equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 15-63°. The S(1)-O(1) bond length is 1.49 Å. The S(1)-O(2) bond length is 1.47 Å. The S(1)-O(4) bond length is 1.47 Å. The S(1)-O(5) bond length is 1.47 Å. In the second S site, S(2) is bonded to one O(3), one O(6), one O(7), and one O(8) atom to form SO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Na(2)O6 octahedra, and  an edgeedge with one Na(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-46°. The S(2)-O(3) bond length is 1.46 Å. The S(2)-O(6) bond length is 1.48 Å. The S(2)-O(7) bond length is 1.50 Å. The S(2)-O(8) bond length is 1.47 Å. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a 4-coordinate geometry to one Na(2), two equivalent Na(1), and one S(1) atom. In the second O site, O(5) is bonded in a 3-coordinate geometry to one Na(3), one Ni(1), and one S(1) atom. In the third O site, O(6) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one S(2) atom. In the fourth O site, O(7) is bonded in a 4-coordinate geometry to one Na(2), one Na(3), one Ni(1), and one S(2) atom. In the fifth O site, O(8) is bonded to one Na(1), one Na(2), one Na(3), and one S(2) atom to form a mixture of distorted edge and corner-sharing ONa3S tetrahedra. In the sixth O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(3), one Ni(1), and one S(1) atom. In the seventh O site, O(2) is bonded to one Na(2), two equivalent Na(3), and one S(1) atom to form a mixture of distorted edge and corner-sharing ONa3S tetrahedra. In the eighth O site, O(3) is bonded in a 4-coordinate geometry to one Na(3), two equivalent Na(1), and one S(2) atom.