MgLa2(NiO3)2 crystallizes in the trigonal R3 space group. Mg(1) is bonded in a trigonal planar geometry to three equivalent O(1) atoms. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. In the second La site, La(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted trigonal planar geometry to three equivalent O(2) atoms. In the second Ni site, Ni(2) is bonded in an octahedral geometry to three equivalent O(1) and three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one La(1), one La(2), and one Ni(2) atom to form distorted OLa2MgNi trigonal pyramids that share corners with four equivalent O(1)La2MgNi trigonal pyramids, corners with seven equivalent O(2)La2Ni2 trigonal pyramids,  an edgeedge with one O(2)La2Ni2 trigonal pyramid, and edges with two equivalent O(1)La2MgNi trigonal pyramids. In the second O site, O(2) is bonded to one La(1), one La(2), one Ni(1), and one Ni(2) atom to form distorted OLa2Ni2 trigonal pyramids that share corners with four equivalent O(2)La2Ni2 trigonal pyramids, corners with seven equivalent O(1)La2MgNi trigonal pyramids,  an edgeedge with one O(1)La2MgNi trigonal pyramid, and edges with two equivalent O(2)La2Ni2 trigonal pyramids.
MgLa2(NiO3)2 crystallizes in the trigonal R3 space group. Mg(1) is bonded in a trigonal planar geometry to three equivalent O(1) atoms. All Mg(1)-O(1) bond lengths are 1.94 Å. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. All La(1)-O(1) bond lengths are 2.35 Å. All La(1)-O(2) bond lengths are 2.53 Å. In the second La site, La(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. All La(2)-O(1) bond lengths are 2.51 Å. All La(2)-O(2) bond lengths are 2.40 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted trigonal planar geometry to three equivalent O(2) atoms. All Ni(1)-O(2) bond lengths are 1.88 Å. In the second Ni site, Ni(2) is bonded in an octahedral geometry to three equivalent O(1) and three equivalent O(2) atoms. All Ni(2)-O(1) bond lengths are 2.13 Å. All Ni(2)-O(2) bond lengths are 2.22 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one La(1), one La(2), and one Ni(2) atom to form distorted OLa2MgNi trigonal pyramids that share corners with four equivalent O(1)La2MgNi trigonal pyramids, corners with seven equivalent O(2)La2Ni2 trigonal pyramids,  an edgeedge with one O(2)La2Ni2 trigonal pyramid, and edges with two equivalent O(1)La2MgNi trigonal pyramids. In the second O site, O(2) is bonded to one La(1), one La(2), one Ni(1), and one Ni(2) atom to form distorted OLa2Ni2 trigonal pyramids that share corners with four equivalent O(2)La2Ni2 trigonal pyramids, corners with seven equivalent O(1)La2MgNi trigonal pyramids,  an edgeedge with one O(1)La2MgNi trigonal pyramid, and edges with two equivalent O(2)La2Ni2 trigonal pyramids.