K4Ni7(AsO4)6 crystallizes in the monoclinic Cm space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to one O(1), one O(11), one O(12), one O(13), one O(2), one O(3), one O(4), one O(6), and one O(7) atom. In the second K site, K(2) is bonded in a 7-coordinate geometry to one O(11), one O(12), one O(8), two equivalent O(4), and two equivalent O(5) atoms. In the third K site, K(3) is bonded in a 7-coordinate geometry to one O(7), two equivalent O(10), two equivalent O(3), and two equivalent O(9) atoms. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(7), one O(8), two equivalent O(10), and two equivalent O(9) atoms to form NiO6 octahedra that share corners with two equivalent Ni(2)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(2)O4 tetrahedra, corners with two equivalent As(3)O4 tetrahedra, and corners with two equivalent As(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-53°. In the second Ni site, Ni(2) is bonded to one O(13), one O(14), one O(2), one O(3), one O(6), and one O(9) atom to form NiO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra,  a cornercorner with one As(3)O4 tetrahedra, corners with two equivalent As(4)O4 tetrahedra,  an edgeedge with one Ni(3)O6 octahedra, and  an edgeedge with one As(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-61°. In the third Ni site, Ni(3) is bonded to one O(1), one O(10), one O(13), one O(14), one O(4), and one O(5) atom to form NiO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(4)O4 tetrahedra, corners with two equivalent As(3)O4 tetrahedra,  an edgeedge with one Ni(2)O6 octahedra, and  an edgeedge with one As(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-60°. In the fourth Ni site, Ni(4) is bonded to one O(1), one O(11), one O(12), one O(2), one O(5), and one O(6) atom to form distorted NiO6 octahedra that share corners with two equivalent Ni(2)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra,  a cornercorner with one As(3)O4 tetrahedra,  a cornercorner with one As(4)O4 tetrahedra,  an edgeedge with one Ni(4)O6 octahedra,  an edgeedge with one As(1)O4 tetrahedra, and  an edgeedge with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-61°. There are four inequivalent As sites. In the first As site, As(1) is bonded to one O(12), one O(8), and two equivalent O(5) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-59°. In the second As site, As(2) is bonded to one O(11), one O(7), and two equivalent O(6) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-59°. In the third As site, As(3) is bonded to one O(14), one O(2), one O(4), and one O(9) atom to form AsO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, and  an edgeedge with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-61°. In the fourth As site, As(4) is bonded to one O(1), one O(10), one O(13), and one O(3) atom to form AsO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, and  an edgeedge with one Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 33-62°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded to one K(1), one Ni(3), one Ni(4), and one As(4) atom to form distorted OKNi2As trigonal pyramids that share corners with two equivalent O(5)KNi2As tetrahedra, corners with two equivalent O(3)K2NiAs trigonal pyramids, and  an edgeedge with one O(11)K3Ni2As octahedra. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one K(1), one Ni(2), one Ni(4), and one As(3) atom. In the third O site, O(3) is bonded to one K(1), one K(3), one Ni(2), and one As(4) atom to form distorted OK2NiAs trigonal pyramids that share  a cornercorner with one O(11)K3Ni2As octahedra,  a cornercorner with one O(3)K2NiAs trigonal pyramid, and corners with two equivalent O(1)KNi2As trigonal pyramids. The corner-sharing octahedral tilt angles are 49°. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one K(1), one K(2), one Ni(3), and one As(3) atom. In the fifth O site, O(5) is bonded to one K(2), one Ni(3), one Ni(4), and one As(1) atom to form distorted OKNi2As tetrahedra that share corners with two equivalent O(1)KNi2As trigonal pyramids,  an edgeedge with one O(11)K3Ni2As octahedra, and  an edgeedge with one O(5)KNi2As tetrahedra. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one K(1), one Ni(2), one Ni(4), and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one K(3), two equivalent K(1), one Ni(1), and one As(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one K(2), one Ni(1), and one As(1) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one K(3), one Ni(1), one Ni(2), and one As(3) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one K(3), one Ni(1), one Ni(3), and one As(4) atom. In the eleventh O site, O(11) is bonded to one K(2), two equivalent K(1), two equivalent Ni(4), and one As(2) atom to form distorted OK3Ni2As octahedra that share corners with two equivalent O(3)K2NiAs trigonal pyramids, edges with two equivalent O(5)KNi2As tetrahedra, and edges with two equivalent O(1)KNi2As trigonal pyramids. In the twelfth O site, O(12) is bonded in a 6-coordinate geometry to one K(2), two equivalent K(1), two equivalent Ni(4), and one As(1) atom. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one K(1), one Ni(2), one Ni(3), and one As(4) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one As(3) atom.
K4Ni7(AsO4)6 crystallizes in the monoclinic Cm space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to one O(1), one O(11), one O(12), one O(13), one O(2), one O(3), one O(4), one O(6), and one O(7) atom. The K(1)-O(1) bond length is 2.73 Å. The K(1)-O(11) bond length is 2.87 Å. The K(1)-O(12) bond length is 3.02 Å. The K(1)-O(13) bond length is 3.01 Å. The K(1)-O(2) bond length is 2.64 Å. The K(1)-O(3) bond length is 2.69 Å. The K(1)-O(4) bond length is 3.17 Å. The K(1)-O(6) bond length is 3.04 Å. The K(1)-O(7) bond length is 3.20 Å. In the second K site, K(2) is bonded in a 7-coordinate geometry to one O(11), one O(12), one O(8), two equivalent O(4), and two equivalent O(5) atoms. The K(2)-O(11) bond length is 2.91 Å. The K(2)-O(12) bond length is 3.24 Å. The K(2)-O(8) bond length is 2.65 Å. Both K(2)-O(4) bond lengths are 2.98 Å. Both K(2)-O(5) bond lengths are 2.74 Å. In the third K site, K(3) is bonded in a 7-coordinate geometry to one O(7), two equivalent O(10), two equivalent O(3), and two equivalent O(9) atoms. The K(3)-O(7) bond length is 3.22 Å. Both K(3)-O(10) bond lengths are 2.68 Å. Both K(3)-O(3) bond lengths are 2.77 Å. Both K(3)-O(9) bond lengths are 2.64 Å. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(7), one O(8), two equivalent O(10), and two equivalent O(9) atoms to form NiO6 octahedra that share corners with two equivalent Ni(2)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(2)O4 tetrahedra, corners with two equivalent As(3)O4 tetrahedra, and corners with two equivalent As(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-53°. The Ni(1)-O(7) bond length is 2.12 Å. The Ni(1)-O(8) bond length is 2.09 Å. Both Ni(1)-O(10) bond lengths are 2.09 Å. Both Ni(1)-O(9) bond lengths are 2.08 Å. In the second Ni site, Ni(2) is bonded to one O(13), one O(14), one O(2), one O(3), one O(6), and one O(9) atom to form NiO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra,  a cornercorner with one As(3)O4 tetrahedra, corners with two equivalent As(4)O4 tetrahedra,  an edgeedge with one Ni(3)O6 octahedra, and  an edgeedge with one As(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-61°. The Ni(2)-O(13) bond length is 2.11 Å. The Ni(2)-O(14) bond length is 2.05 Å. The Ni(2)-O(2) bond length is 2.15 Å. The Ni(2)-O(3) bond length is 2.10 Å. The Ni(2)-O(6) bond length is 2.10 Å. The Ni(2)-O(9) bond length is 2.12 Å. In the third Ni site, Ni(3) is bonded to one O(1), one O(10), one O(13), one O(14), one O(4), and one O(5) atom to form NiO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra,  a cornercorner with one As(4)O4 tetrahedra, corners with two equivalent As(3)O4 tetrahedra,  an edgeedge with one Ni(2)O6 octahedra, and  an edgeedge with one As(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-60°. The Ni(3)-O(1) bond length is 2.20 Å. The Ni(3)-O(10) bond length is 2.09 Å. The Ni(3)-O(13) bond length is 2.06 Å. The Ni(3)-O(14) bond length is 2.08 Å. The Ni(3)-O(4) bond length is 2.10 Å. The Ni(3)-O(5) bond length is 2.07 Å. In the fourth Ni site, Ni(4) is bonded to one O(1), one O(11), one O(12), one O(2), one O(5), and one O(6) atom to form distorted NiO6 octahedra that share corners with two equivalent Ni(2)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra,  a cornercorner with one As(3)O4 tetrahedra,  a cornercorner with one As(4)O4 tetrahedra,  an edgeedge with one Ni(4)O6 octahedra,  an edgeedge with one As(1)O4 tetrahedra, and  an edgeedge with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-61°. The Ni(4)-O(1) bond length is 2.08 Å. The Ni(4)-O(11) bond length is 2.36 Å. The Ni(4)-O(12) bond length is 2.36 Å. The Ni(4)-O(2) bond length is 2.08 Å. The Ni(4)-O(5) bond length is 2.09 Å. The Ni(4)-O(6) bond length is 2.11 Å. There are four inequivalent As sites. In the first As site, As(1) is bonded to one O(12), one O(8), and two equivalent O(5) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-59°. The As(1)-O(12) bond length is 1.74 Å. The As(1)-O(8) bond length is 1.69 Å. Both As(1)-O(5) bond lengths are 1.74 Å. In the second As site, As(2) is bonded to one O(11), one O(7), and two equivalent O(6) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 57-59°. The As(2)-O(11) bond length is 1.75 Å. The As(2)-O(7) bond length is 1.70 Å. Both As(2)-O(6) bond lengths are 1.74 Å. In the third As site, As(3) is bonded to one O(14), one O(2), one O(4), and one O(9) atom to form AsO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, and  an edgeedge with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 29-61°. The As(3)-O(14) bond length is 1.72 Å. The As(3)-O(2) bond length is 1.77 Å. The As(3)-O(4) bond length is 1.70 Å. The As(3)-O(9) bond length is 1.74 Å. In the fourth As site, As(4) is bonded to one O(1), one O(10), one O(13), and one O(3) atom to form AsO4 tetrahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra,  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, and  an edgeedge with one Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 33-62°. The As(4)-O(1) bond length is 1.75 Å. The As(4)-O(10) bond length is 1.75 Å. The As(4)-O(13) bond length is 1.73 Å. The As(4)-O(3) bond length is 1.70 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded to one K(1), one Ni(3), one Ni(4), and one As(4) atom to form distorted OKNi2As trigonal pyramids that share corners with two equivalent O(5)KNi2As tetrahedra, corners with two equivalent O(3)K2NiAs trigonal pyramids, and  an edgeedge with one O(11)K3Ni2As octahedra. In the second O site, O(2) is bonded in a distorted see-saw-like geometry to one K(1), one Ni(2), one Ni(4), and one As(3) atom. In the third O site, O(3) is bonded to one K(1), one K(3), one Ni(2), and one As(4) atom to form distorted OK2NiAs trigonal pyramids that share  a cornercorner with one O(11)K3Ni2As octahedra,  a cornercorner with one O(3)K2NiAs trigonal pyramid, and corners with two equivalent O(1)KNi2As trigonal pyramids. The corner-sharing octahedral tilt angles are 49°. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one K(1), one K(2), one Ni(3), and one As(3) atom. In the fifth O site, O(5) is bonded to one K(2), one Ni(3), one Ni(4), and one As(1) atom to form distorted OKNi2As tetrahedra that share corners with two equivalent O(1)KNi2As trigonal pyramids,  an edgeedge with one O(11)K3Ni2As octahedra, and  an edgeedge with one O(5)KNi2As tetrahedra. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one K(1), one Ni(2), one Ni(4), and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one K(3), two equivalent K(1), one Ni(1), and one As(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one K(2), one Ni(1), and one As(1) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one K(3), one Ni(1), one Ni(2), and one As(3) atom. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one K(3), one Ni(1), one Ni(3), and one As(4) atom. In the eleventh O site, O(11) is bonded to one K(2), two equivalent K(1), two equivalent Ni(4), and one As(2) atom to form distorted OK3Ni2As octahedra that share corners with two equivalent O(3)K2NiAs trigonal pyramids, edges with two equivalent O(5)KNi2As tetrahedra, and edges with two equivalent O(1)KNi2As trigonal pyramids. In the twelfth O site, O(12) is bonded in a 6-coordinate geometry to one K(2), two equivalent K(1), two equivalent Ni(4), and one As(1) atom. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one K(1), one Ni(2), one Ni(3), and one As(4) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one As(3) atom.