MgNi4O9 crystallizes in the triclinic P1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(12), one O(13), one O(14), one O(7), one O(8), and one O(9) atom. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to one O(15), one O(16), one O(17), one O(18), one O(3), one O(4), one O(5), and one O(6) atom. There are eight inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(13), one O(14), one O(17), and one O(8) atom to form a mixture of distorted corner and edge-sharing NiO5 trigonal bipyramids. In the second Ni site, Ni(2) is bonded to one O(1), one O(11), one O(17), one O(18), and one O(6) atom to form a mixture of distorted corner and edge-sharing NiO5 trigonal bipyramids. In the third Ni site, Ni(3) is bonded to one O(12), one O(14), one O(15), one O(2), and one O(7) atom to form a mixture of distorted corner and edge-sharing NiO5 square pyramids. In the fourth Ni site, Ni(4) is bonded to one O(12), one O(16), one O(18), one O(2), and one O(5) atom to form a mixture of distorted corner and edge-sharing NiO5 trigonal bipyramids. In the fifth Ni site, Ni(5) is bonded to one O(1), one O(11), one O(12), one O(16), and one O(9) atom to form a mixture of corner and edge-sharing NiO5 trigonal bipyramids. In the sixth Ni site, Ni(6) is bonded to one O(10), one O(11), one O(13), one O(18), and one O(2) atom to form a mixture of corner and edge-sharing NiO5 trigonal bipyramids. In the seventh Ni site, Ni(7) is bonded to one O(13), one O(15), one O(17), one O(2), and one O(4) atom to form a mixture of corner and edge-sharing NiO5 trigonal bipyramids. In the eighth Ni site, Ni(8) is bonded to one O(1), one O(14), one O(15), one O(16), and one O(3) atom to form a mixture of corner and edge-sharing NiO5 trigonal bipyramids. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ni(1), one Ni(2), one Ni(5), and one Ni(8) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ni(3), one Ni(4), one Ni(6), and one Ni(7) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one Ni(8), and one O(4) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(2), one Ni(7), and one O(3) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(2), one Ni(4), and one O(6) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(2), one Ni(2), and one O(5) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(3), and one O(8) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(1), and one O(7) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(5), and one O(10) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(6), and one O(9) atom. In the eleventh O site, O(11) is bonded in a see-saw-like geometry to one Mg(1), one Ni(2), one Ni(5), and one Ni(6) atom. In the twelfth O site, O(12) is bonded in a distorted see-saw-like geometry to one Mg(1), one Ni(3), one Ni(4), and one Ni(5) atom. In the thirteenth O site, O(13) is bonded in a see-saw-like geometry to one Mg(1), one Ni(1), one Ni(6), and one Ni(7) atom. In the fourteenth O site, O(14) is bonded in a see-saw-like geometry to one Mg(1), one Ni(1), one Ni(3), and one Ni(8) atom. In the fifteenth O site, O(15) is bonded in a see-saw-like geometry to one Mg(2), one Ni(3), one Ni(7), and one Ni(8) atom. In the sixteenth O site, O(16) is bonded in a see-saw-like geometry to one Mg(2), one Ni(4), one Ni(5), and one Ni(8) atom. In the seventeenth O site, O(17) is bonded in a distorted see-saw-like geometry to one Mg(2), one Ni(1), one Ni(2), and one Ni(7) atom. In the eighteenth O site, O(18) is bonded in a see-saw-like geometry to one Mg(2), one Ni(2), one Ni(4), and one Ni(6) atom.
MgNi4O9 crystallizes in the triclinic P1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(12), one O(13), one O(14), one O(7), one O(8), and one O(9) atom. The Mg(1)-O(10) bond length is 2.46 Å. The Mg(1)-O(11) bond length is 2.14 Å. The Mg(1)-O(12) bond length is 2.07 Å. The Mg(1)-O(13) bond length is 2.10 Å. The Mg(1)-O(14) bond length is 2.13 Å. The Mg(1)-O(7) bond length is 2.19 Å. The Mg(1)-O(8) bond length is 2.20 Å. The Mg(1)-O(9) bond length is 2.51 Å. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to one O(15), one O(16), one O(17), one O(18), one O(3), one O(4), one O(5), and one O(6) atom. The Mg(2)-O(15) bond length is 2.15 Å. The Mg(2)-O(16) bond length is 2.12 Å. The Mg(2)-O(17) bond length is 2.06 Å. The Mg(2)-O(18) bond length is 2.11 Å. The Mg(2)-O(3) bond length is 2.46 Å. The Mg(2)-O(4) bond length is 2.46 Å. The Mg(2)-O(5) bond length is 2.15 Å. The Mg(2)-O(6) bond length is 2.13 Å. There are eight inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(13), one O(14), one O(17), and one O(8) atom to form a mixture of distorted corner and edge-sharing NiO5 trigonal bipyramids. The Ni(1)-O(1) bond length is 2.07 Å. The Ni(1)-O(13) bond length is 1.99 Å. The Ni(1)-O(14) bond length is 1.94 Å. The Ni(1)-O(17) bond length is 1.96 Å. The Ni(1)-O(8) bond length is 2.04 Å. In the second Ni site, Ni(2) is bonded to one O(1), one O(11), one O(17), one O(18), and one O(6) atom to form a mixture of distorted corner and edge-sharing NiO5 trigonal bipyramids. The Ni(2)-O(1) bond length is 1.99 Å. The Ni(2)-O(11) bond length is 2.03 Å. The Ni(2)-O(17) bond length is 1.97 Å. The Ni(2)-O(18) bond length is 1.95 Å. The Ni(2)-O(6) bond length is 2.02 Å. In the third Ni site, Ni(3) is bonded to one O(12), one O(14), one O(15), one O(2), and one O(7) atom to form a mixture of distorted corner and edge-sharing NiO5 square pyramids. The Ni(3)-O(12) bond length is 2.00 Å. The Ni(3)-O(14) bond length is 1.95 Å. The Ni(3)-O(15) bond length is 2.03 Å. The Ni(3)-O(2) bond length is 2.01 Å. The Ni(3)-O(7) bond length is 2.02 Å. In the fourth Ni site, Ni(4) is bonded to one O(12), one O(16), one O(18), one O(2), and one O(5) atom to form a mixture of distorted corner and edge-sharing NiO5 trigonal bipyramids. The Ni(4)-O(12) bond length is 1.97 Å. The Ni(4)-O(16) bond length is 1.99 Å. The Ni(4)-O(18) bond length is 1.93 Å. The Ni(4)-O(2) bond length is 2.05 Å. The Ni(4)-O(5) bond length is 2.05 Å. In the fifth Ni site, Ni(5) is bonded to one O(1), one O(11), one O(12), one O(16), and one O(9) atom to form a mixture of corner and edge-sharing NiO5 trigonal bipyramids. The Ni(5)-O(1) bond length is 1.89 Å. The Ni(5)-O(11) bond length is 1.85 Å. The Ni(5)-O(12) bond length is 1.86 Å. The Ni(5)-O(16) bond length is 1.89 Å. The Ni(5)-O(9) bond length is 2.08 Å. In the sixth Ni site, Ni(6) is bonded to one O(10), one O(11), one O(13), one O(18), and one O(2) atom to form a mixture of corner and edge-sharing NiO5 trigonal bipyramids. The Ni(6)-O(10) bond length is 2.08 Å. The Ni(6)-O(11) bond length is 1.94 Å. The Ni(6)-O(13) bond length is 1.90 Å. The Ni(6)-O(18) bond length is 1.90 Å. The Ni(6)-O(2) bond length is 1.94 Å. In the seventh Ni site, Ni(7) is bonded to one O(13), one O(15), one O(17), one O(2), and one O(4) atom to form a mixture of corner and edge-sharing NiO5 trigonal bipyramids. The Ni(7)-O(13) bond length is 1.93 Å. The Ni(7)-O(15) bond length is 1.88 Å. The Ni(7)-O(17) bond length is 1.89 Å. The Ni(7)-O(2) bond length is 1.93 Å. The Ni(7)-O(4) bond length is 2.09 Å. In the eighth Ni site, Ni(8) is bonded to one O(1), one O(14), one O(15), one O(16), and one O(3) atom to form a mixture of corner and edge-sharing NiO5 trigonal bipyramids. The Ni(8)-O(1) bond length is 1.93 Å. The Ni(8)-O(14) bond length is 1.90 Å. The Ni(8)-O(15) bond length is 1.91 Å. The Ni(8)-O(16) bond length is 1.91 Å. The Ni(8)-O(3) bond length is 2.08 Å. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ni(1), one Ni(2), one Ni(5), and one Ni(8) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ni(3), one Ni(4), one Ni(6), and one Ni(7) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one Ni(8), and one O(4) atom. The O(3)-O(4) bond length is 1.33 Å. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(2), one Ni(7), and one O(3) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(2), one Ni(4), and one O(6) atom. The O(5)-O(6) bond length is 1.36 Å. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(2), one Ni(2), and one O(5) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(3), and one O(8) atom. The O(7)-O(8) bond length is 1.36 Å. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(1), and one O(7) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(5), and one O(10) atom. The O(9)-O(10) bond length is 1.32 Å. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Mg(1), one Ni(6), and one O(9) atom. In the eleventh O site, O(11) is bonded in a see-saw-like geometry to one Mg(1), one Ni(2), one Ni(5), and one Ni(6) atom. In the twelfth O site, O(12) is bonded in a distorted see-saw-like geometry to one Mg(1), one Ni(3), one Ni(4), and one Ni(5) atom. In the thirteenth O site, O(13) is bonded in a see-saw-like geometry to one Mg(1), one Ni(1), one Ni(6), and one Ni(7) atom. In the fourteenth O site, O(14) is bonded in a see-saw-like geometry to one Mg(1), one Ni(1), one Ni(3), and one Ni(8) atom. In the fifteenth O site, O(15) is bonded in a see-saw-like geometry to one Mg(2), one Ni(3), one Ni(7), and one Ni(8) atom. In the sixteenth O site, O(16) is bonded in a see-saw-like geometry to one Mg(2), one Ni(4), one Ni(5), and one Ni(8) atom. In the seventeenth O site, O(17) is bonded in a distorted see-saw-like geometry to one Mg(2), one Ni(1), one Ni(2), and one Ni(7) atom. In the eighteenth O site, O(18) is bonded in a see-saw-like geometry to one Mg(2), one Ni(2), one Ni(4), and one Ni(6) atom.