Na14Ni2O9 crystallizes in the triclinic P-1 space group. There are fourteen inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(10), one O(2), one O(5), and one O(7) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra, and  an edgeedge with one Na(8)O4 tetrahedra. In the second Na site, Na(2) is bonded to one O(1), one O(6), one O(8), and one O(9) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra, corners with three equivalent Ni(1)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Na(9)O4 tetrahedra. In the third Na site, Na(3) is bonded to one O(1), one O(8), and two equivalent O(4) atoms to form NaO4 tetrahedra that share  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra, corners with four equivalent Na(5)O4 tetrahedra, corners with four equivalent Na(7)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. In the fourth Na site, Na(4) is bonded to one O(2), one O(7), and two equivalent O(3) atoms to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with four equivalent Na(6)O4 tetrahedra, corners with four equivalent Na(8)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. In the fifth Na site, Na(5) is bonded to one O(1), one O(9), and two equivalent O(4) atoms to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra, corners with four equivalent Na(3)O4 tetrahedra, corners with four equivalent Na(7)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. In the sixth Na site, Na(6) is bonded to one O(10), one O(2), and two equivalent O(3) atoms to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with four equivalent Na(4)O4 tetrahedra, corners with four equivalent Na(8)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. In the seventh Na site, Na(7) is bonded to one O(1), one O(6), and two equivalent O(4) atoms to form NaO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra, corners with four equivalent Na(3)O4 tetrahedra, corners with four equivalent Na(5)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. In the eighth Na site, Na(8) is bonded to one O(2), one O(5), and two equivalent O(3) atoms to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with four equivalent Na(4)O4 tetrahedra, corners with four equivalent Na(6)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. In the ninth Na site, Na(9) is bonded to one O(5), one O(6), one O(8), and one O(9) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(11)O4 tetrahedra, corners with three equivalent Na(14)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. In the tenth Na site, Na(10) is bonded to one O(10), one O(5), one O(6), and one O(7) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(12)O4 tetrahedra, corners with three equivalent Na(13)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(9)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. In the eleventh Na site, Na(11) is bonded to one O(6), one O(7), one O(8), and one O(9) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(14)O4 tetrahedra, corners with three equivalent Na(9)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. In the twelfth Na site, Na(12) is bonded to one O(10), one O(5), one O(7), and one O(8) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(10)O4 tetrahedra, corners with three equivalent Na(13)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(9)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. In the thirteenth Na site, Na(13) is bonded to one O(10), one O(5), one O(7), and one O(9) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(10)O4 tetrahedra, corners with three equivalent Na(12)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(9)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. In the fourteenth Na site, Na(14) is bonded to one O(10), one O(6), one O(8), and one O(9) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(11)O4 tetrahedra, corners with three equivalent Na(9)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(4), one O(6), one O(8), and one O(9) atom to form NiO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra, corners with three equivalent Na(2)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Na(9)O4 tetrahedra. In the second Ni site, Ni(2) is bonded to one O(10), one O(3), one O(5), and one O(7) atom to form NiO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra, corners with three equivalent Na(1)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra, and  an edgeedge with one Na(8)O4 tetrahedra. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a body-centered cubic geometry to two equivalent Na(2), two equivalent Na(3), two equivalent Na(5), and two equivalent Na(7) atoms. In the second O site, O(2) is bonded in a body-centered cubic geometry to two equivalent Na(1), two equivalent Na(4), two equivalent Na(6), and two equivalent Na(8) atoms. In the third O site, O(3) is bonded in a 7-coordinate geometry to two equivalent Na(4), two equivalent Na(6), two equivalent Na(8), and one Ni(2) atom. In the fourth O site, O(4) is bonded in a 7-coordinate geometry to two equivalent Na(3), two equivalent Na(5), two equivalent Na(7), and one Ni(1) atom. In the fifth O site, O(5) is bonded to one Na(1), one Na(10), one Na(12), one Na(13), one Na(8), one Na(9), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the sixth O site, O(6) is bonded to one Na(10), one Na(11), one Na(14), one Na(2), one Na(7), one Na(9), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the seventh O site, O(7) is bonded to one Na(1), one Na(10), one Na(11), one Na(12), one Na(13), one Na(4), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the eighth O site, O(8) is bonded to one Na(11), one Na(12), one Na(14), one Na(2), one Na(3), one Na(9), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the ninth O site, O(9) is bonded to one Na(11), one Na(13), one Na(14), one Na(2), one Na(5), one Na(9), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the tenth O site, O(10) is bonded to one Na(1), one Na(10), one Na(12), one Na(13), one Na(14), one Na(6), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids.
Na14Ni2O9 crystallizes in the triclinic P-1 space group. There are fourteen inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(10), one O(2), one O(5), and one O(7) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra, and  an edgeedge with one Na(8)O4 tetrahedra. The Na(1)-O(10) bond length is 2.39 Å. The Na(1)-O(2) bond length is 2.36 Å. The Na(1)-O(5) bond length is 2.38 Å. The Na(1)-O(7) bond length is 2.40 Å. In the second Na site, Na(2) is bonded to one O(1), one O(6), one O(8), and one O(9) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra, corners with three equivalent Ni(1)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Na(9)O4 tetrahedra. The Na(2)-O(1) bond length is 2.35 Å. The Na(2)-O(6) bond length is 2.39 Å. The Na(2)-O(8) bond length is 2.37 Å. The Na(2)-O(9) bond length is 2.38 Å. In the third Na site, Na(3) is bonded to one O(1), one O(8), and two equivalent O(4) atoms to form NaO4 tetrahedra that share  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra, corners with four equivalent Na(5)O4 tetrahedra, corners with four equivalent Na(7)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. The Na(3)-O(1) bond length is 2.44 Å. The Na(3)-O(8) bond length is 2.36 Å. There is one shorter (2.38 Å) and one longer (2.41 Å) Na(3)-O(4) bond length. In the fourth Na site, Na(4) is bonded to one O(2), one O(7), and two equivalent O(3) atoms to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with four equivalent Na(6)O4 tetrahedra, corners with four equivalent Na(8)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. The Na(4)-O(2) bond length is 2.44 Å. The Na(4)-O(7) bond length is 2.37 Å. There is one shorter (2.36 Å) and one longer (2.42 Å) Na(4)-O(3) bond length. In the fifth Na site, Na(5) is bonded to one O(1), one O(9), and two equivalent O(4) atoms to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra, corners with four equivalent Na(3)O4 tetrahedra, corners with four equivalent Na(7)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. The Na(5)-O(1) bond length is 2.46 Å. The Na(5)-O(9) bond length is 2.35 Å. There is one shorter (2.39 Å) and one longer (2.40 Å) Na(5)-O(4) bond length. In the sixth Na site, Na(6) is bonded to one O(10), one O(2), and two equivalent O(3) atoms to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with four equivalent Na(4)O4 tetrahedra, corners with four equivalent Na(8)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. The Na(6)-O(10) bond length is 2.37 Å. The Na(6)-O(2) bond length is 2.45 Å. There is one shorter (2.36 Å) and one longer (2.42 Å) Na(6)-O(3) bond length. In the seventh Na site, Na(7) is bonded to one O(1), one O(6), and two equivalent O(4) atoms to form NaO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra, corners with four equivalent Na(3)O4 tetrahedra, corners with four equivalent Na(5)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. The Na(7)-O(1) bond length is 2.45 Å. The Na(7)-O(6) bond length is 2.34 Å. There is one shorter (2.38 Å) and one longer (2.41 Å) Na(7)-O(4) bond length. In the eighth Na site, Na(8) is bonded to one O(2), one O(5), and two equivalent O(3) atoms to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with four equivalent Na(4)O4 tetrahedra, corners with four equivalent Na(6)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra,  an edgeedge with one Na(8)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. The Na(8)-O(2) bond length is 2.44 Å. The Na(8)-O(5) bond length is 2.36 Å. There is one shorter (2.36 Å) and one longer (2.42 Å) Na(8)-O(3) bond length. In the ninth Na site, Na(9) is bonded to one O(5), one O(6), one O(8), and one O(9) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(11)O4 tetrahedra, corners with three equivalent Na(14)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. The Na(9)-O(5) bond length is 2.41 Å. The Na(9)-O(6) bond length is 2.33 Å. The Na(9)-O(8) bond length is 2.34 Å. The Na(9)-O(9) bond length is 2.39 Å. In the tenth Na site, Na(10) is bonded to one O(10), one O(5), one O(6), and one O(7) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(12)O4 tetrahedra, corners with three equivalent Na(13)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(9)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. The Na(10)-O(10) bond length is 2.39 Å. The Na(10)-O(5) bond length is 2.35 Å. The Na(10)-O(6) bond length is 2.41 Å. The Na(10)-O(7) bond length is 2.37 Å. In the eleventh Na site, Na(11) is bonded to one O(6), one O(7), one O(8), and one O(9) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(14)O4 tetrahedra, corners with three equivalent Na(9)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. The Na(11)-O(6) bond length is 2.44 Å. The Na(11)-O(7) bond length is 2.39 Å. The Na(11)-O(8) bond length is 2.37 Å. The Na(11)-O(9) bond length is 2.35 Å. In the twelfth Na site, Na(12) is bonded to one O(10), one O(5), one O(7), and one O(8) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(10)O4 tetrahedra, corners with three equivalent Na(13)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(9)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. The Na(12)-O(10) bond length is 2.36 Å. The Na(12)-O(5) bond length is 2.40 Å. The Na(12)-O(7) bond length is 2.35 Å. The Na(12)-O(8) bond length is 2.40 Å. In the thirteenth Na site, Na(13) is bonded to one O(10), one O(5), one O(7), and one O(9) atom to form NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(10)O4 tetrahedra, corners with three equivalent Na(12)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(9)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. The Na(13)-O(10) bond length is 2.35 Å. The Na(13)-O(5) bond length is 2.36 Å. The Na(13)-O(7) bond length is 2.39 Å. The Na(13)-O(9) bond length is 2.41 Å. In the fourteenth Na site, Na(14) is bonded to one O(10), one O(6), one O(8), and one O(9) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Ni(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra, corners with three equivalent Na(11)O4 tetrahedra, corners with three equivalent Na(9)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(2)O4 tetrahedra, and  an edgeedge with one Ni(1)O4 tetrahedra. The Na(14)-O(10) bond length is 2.40 Å. The Na(14)-O(6) bond length is 2.34 Å. The Na(14)-O(8) bond length is 2.40 Å. The Na(14)-O(9) bond length is 2.35 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(4), one O(6), one O(8), and one O(9) atom to form NiO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(3)O4 tetrahedra,  a cornercorner with one Na(5)O4 tetrahedra,  a cornercorner with one Na(7)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra, corners with three equivalent Na(2)O4 tetrahedra,  an edgeedge with one Na(11)O4 tetrahedra,  an edgeedge with one Na(14)O4 tetrahedra,  an edgeedge with one Na(3)O4 tetrahedra,  an edgeedge with one Na(5)O4 tetrahedra,  an edgeedge with one Na(7)O4 tetrahedra, and  an edgeedge with one Na(9)O4 tetrahedra. The Ni(1)-O(4) bond length is 2.05 Å. The Ni(1)-O(6) bond length is 2.05 Å. The Ni(1)-O(8) bond length is 2.07 Å. The Ni(1)-O(9) bond length is 2.05 Å. In the second Ni site, Ni(2) is bonded to one O(10), one O(3), one O(5), and one O(7) atom to form NiO4 tetrahedra that share  a cornercorner with one Na(10)O4 tetrahedra,  a cornercorner with one Na(11)O4 tetrahedra,  a cornercorner with one Na(12)O4 tetrahedra,  a cornercorner with one Na(13)O4 tetrahedra,  a cornercorner with one Na(14)O4 tetrahedra,  a cornercorner with one Na(4)O4 tetrahedra,  a cornercorner with one Na(6)O4 tetrahedra,  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Na(9)O4 tetrahedra, corners with three equivalent Na(1)O4 tetrahedra,  an edgeedge with one Na(10)O4 tetrahedra,  an edgeedge with one Na(12)O4 tetrahedra,  an edgeedge with one Na(13)O4 tetrahedra,  an edgeedge with one Na(4)O4 tetrahedra,  an edgeedge with one Na(6)O4 tetrahedra, and  an edgeedge with one Na(8)O4 tetrahedra. The Ni(2)-O(10) bond length is 2.05 Å. The Ni(2)-O(3) bond length is 2.07 Å. The Ni(2)-O(5) bond length is 2.05 Å. The Ni(2)-O(7) bond length is 2.05 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a body-centered cubic geometry to two equivalent Na(2), two equivalent Na(3), two equivalent Na(5), and two equivalent Na(7) atoms. In the second O site, O(2) is bonded in a body-centered cubic geometry to two equivalent Na(1), two equivalent Na(4), two equivalent Na(6), and two equivalent Na(8) atoms. In the third O site, O(3) is bonded in a 7-coordinate geometry to two equivalent Na(4), two equivalent Na(6), two equivalent Na(8), and one Ni(2) atom. In the fourth O site, O(4) is bonded in a 7-coordinate geometry to two equivalent Na(3), two equivalent Na(5), two equivalent Na(7), and one Ni(1) atom. In the fifth O site, O(5) is bonded to one Na(1), one Na(10), one Na(12), one Na(13), one Na(8), one Na(9), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the sixth O site, O(6) is bonded to one Na(10), one Na(11), one Na(14), one Na(2), one Na(7), one Na(9), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the seventh O site, O(7) is bonded to one Na(1), one Na(10), one Na(11), one Na(12), one Na(13), one Na(4), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the eighth O site, O(8) is bonded to one Na(11), one Na(12), one Na(14), one Na(2), one Na(3), one Na(9), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the ninth O site, O(9) is bonded to one Na(11), one Na(13), one Na(14), one Na(2), one Na(5), one Na(9), and one Ni(1) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids. In the tenth O site, O(10) is bonded to one Na(1), one Na(10), one Na(12), one Na(13), one Na(14), one Na(6), and one Ni(2) atom to form a mixture of distorted corner and edge-sharing ONa6Ni pentagonal bipyramids.