MgLa4NiO8 crystallizes in the orthorhombic Cmmm space group. Mg(1) is bonded in a square co-planar geometry to four equivalent O(2) atoms. There are two inequivalent La sites. In the first La site, La(1) is bonded to two equivalent O(3) and three equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing LaO5 square pyramids. In the second La site, La(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. Ni(1) is bonded in a distorted square co-planar geometry to two equivalent O(3) and four equivalent O(2) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent La(2) and three equivalent La(1) atoms to form a mixture of distorted corner and edge-sharing OLa5 trigonal bipyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent La(2), and one Ni(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent La(1), two equivalent La(2), and one Ni(1) atom.
MgLa4NiO8 crystallizes in the orthorhombic Cmmm space group. Mg(1) is bonded in a square co-planar geometry to four equivalent O(2) atoms. All Mg(1)-O(2) bond lengths are 1.92 Å. There are two inequivalent La sites. In the first La site, La(1) is bonded to two equivalent O(3) and three equivalent O(1) atoms to form a mixture of distorted corner and edge-sharing LaO5 square pyramids. Both La(1)-O(3) bond lengths are 2.60 Å. There is one shorter (2.18 Å) and two longer (2.69 Å) La(1)-O(1) bond lengths. In the second La site, La(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. Both La(2)-O(1) bond lengths are 3.01 Å. Both La(2)-O(3) bond lengths are 2.83 Å. All La(2)-O(2) bond lengths are 2.41 Å. Ni(1) is bonded in a distorted square co-planar geometry to two equivalent O(3) and four equivalent O(2) atoms. Both Ni(1)-O(3) bond lengths are 2.56 Å. All Ni(1)-O(2) bond lengths are 1.91 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent La(2) and three equivalent La(1) atoms to form a mixture of distorted corner and edge-sharing OLa5 trigonal bipyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent La(2), and one Ni(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent La(1), two equivalent La(2), and one Ni(1) atom.