Mg2LaTaO6 crystallizes in the orthorhombic Imma space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a square co-planar geometry to four equivalent O(3) atoms. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(2) atoms. La(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form distorted LaO6 octahedra that share corners with two equivalent La(1)O6 octahedra and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles are 77°. Ta(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra and edges with two equivalent La(1)O6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(2) and two equivalent La(1) atoms to form OLa2Mg2 tetrahedra that share corners with two equivalent O(2)Mg2Ta2 tetrahedra, corners with four equivalent O(1)La2Mg2 tetrahedra, and  an edgeedge with one O(2)Mg2Ta2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Mg(2) and two equivalent Ta(1) atoms to form distorted OMg2Ta2 tetrahedra that share corners with two equivalent O(1)La2Mg2 tetrahedra, corners with four equivalent O(2)Mg2Ta2 tetrahedra, and  an edgeedge with one O(1)La2Mg2 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one La(1), and one Ta(1) atom.
Mg2LaTaO6 crystallizes in the orthorhombic Imma space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a square co-planar geometry to four equivalent O(3) atoms. All Mg(1)-O(3) bond lengths are 1.98 Å. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(2) atoms. Both Mg(2)-O(1) bond lengths are 2.04 Å. Both Mg(2)-O(2) bond lengths are 2.51 Å. La(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form distorted LaO6 octahedra that share corners with two equivalent La(1)O6 octahedra and edges with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles are 77°. Both La(1)-O(1) bond lengths are 2.43 Å. All La(1)-O(3) bond lengths are 2.39 Å. Ta(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra and edges with two equivalent La(1)O6 octahedra. The corner-sharing octahedral tilt angles are 45°. Both Ta(1)-O(2) bond lengths are 2.06 Å. All Ta(1)-O(3) bond lengths are 1.99 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(2) and two equivalent La(1) atoms to form OLa2Mg2 tetrahedra that share corners with two equivalent O(2)Mg2Ta2 tetrahedra, corners with four equivalent O(1)La2Mg2 tetrahedra, and  an edgeedge with one O(2)Mg2Ta2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Mg(2) and two equivalent Ta(1) atoms to form distorted OMg2Ta2 tetrahedra that share corners with two equivalent O(1)La2Mg2 tetrahedra, corners with four equivalent O(2)Mg2Ta2 tetrahedra, and  an edgeedge with one O(1)La2Mg2 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one La(1), and one Ta(1) atom.