BaMgNdCo2O5 crystallizes in the orthorhombic Pmm2 space group. Ba(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(5) atoms. Mg(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Nd(1)O6 octahedra, corners with four equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Nd(1)O6 octahedra. The corner-sharing octahedral tilt angles are 5°. Nd(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted NdO6 octahedra that share corners with two equivalent Nd(1)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, edges with two equivalent Nd(1)O6 octahedra,  an edgeedge with one Mg(1)O4 tetrahedra, and edges with four equivalent Co(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 53°. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(3) atoms. In the second Co site, Co(2) is bonded to one O(5), two equivalent O(2), and two equivalent O(4) atoms to form CoO5 trigonal bipyramids that share corners with four equivalent Co(2)O5 trigonal bipyramids and edges with four equivalent Nd(1)O6 octahedra. There are five inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Nd(1) atoms. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Nd(1), and two equivalent Co(2) atoms to form distorted OBa2Nd2Co2 octahedra that share corners with two equivalent O(2)Ba2Nd2Co2 octahedra, corners with four equivalent O(5)Ba4Co2 octahedra, edges with two equivalent O(2)Ba2Nd2Co2 octahedra, edges with four equivalent O(4)Nd2Co2 tetrahedra, and faces with two equivalent O(5)Ba4Co2 octahedra. The corner-sharing octahedral tilt angles range from 12-61°. In the third O site, O(3) is bonded to two equivalent Mg(1) and two equivalent Co(1) atoms to form distorted OMg2Co2 trigonal pyramids that share corners with two equivalent O(5)Ba4Co2 octahedra and corners with four equivalent O(3)Mg2Co2 trigonal pyramids. The corner-sharing octahedral tilt angles are 66°. In the fourth O site, O(4) is bonded to two equivalent Nd(1) and two equivalent Co(2) atoms to form distorted ONd2Co2 tetrahedra that share corners with two equivalent O(5)Ba4Co2 octahedra, corners with four equivalent O(4)Nd2Co2 tetrahedra, and edges with four equivalent O(2)Ba2Nd2Co2 octahedra. The corner-sharing octahedral tilt angles are 64°. In the fifth O site, O(5) is bonded to four equivalent Ba(1), one Co(1), and one Co(2) atom to form OBa4Co2 octahedra that share corners with four equivalent O(2)Ba2Nd2Co2 octahedra, corners with four equivalent O(5)Ba4Co2 octahedra, corners with two equivalent O(4)Nd2Co2 tetrahedra, corners with two equivalent O(3)Mg2Co2 trigonal pyramids, edges with four equivalent O(5)Ba4Co2 octahedra, and faces with two equivalent O(2)Ba2Nd2Co2 octahedra. The corner-sharing octahedral tilt angles range from 9-61°.
BaMgNdCo2O5 crystallizes in the orthorhombic Pmm2 space group. Ba(1) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(5) atoms. Both Ba(1)-O(2) bond lengths are 2.81 Å. All Ba(1)-O(5) bond lengths are 2.74 Å. Mg(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Nd(1)O6 octahedra, corners with four equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Nd(1)O6 octahedra. The corner-sharing octahedral tilt angles are 5°. Both Mg(1)-O(1) bond lengths are 2.26 Å. Both Mg(1)-O(3) bond lengths are 2.15 Å. Nd(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted NdO6 octahedra that share corners with two equivalent Nd(1)O6 octahedra, corners with two equivalent Mg(1)O4 tetrahedra, edges with two equivalent Nd(1)O6 octahedra,  an edgeedge with one Mg(1)O4 tetrahedra, and edges with four equivalent Co(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 53°. Both Nd(1)-O(1) bond lengths are 2.43 Å. Both Nd(1)-O(2) bond lengths are 2.46 Å. Both Nd(1)-O(4) bond lengths are 2.29 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(3) atoms. The Co(1)-O(5) bond length is 1.96 Å. Both Co(1)-O(3) bond lengths are 1.97 Å. In the second Co site, Co(2) is bonded to one O(5), two equivalent O(2), and two equivalent O(4) atoms to form CoO5 trigonal bipyramids that share corners with four equivalent Co(2)O5 trigonal bipyramids and edges with four equivalent Nd(1)O6 octahedra. The Co(2)-O(5) bond length is 2.17 Å. Both Co(2)-O(2) bond lengths are 2.06 Å. Both Co(2)-O(4) bond lengths are 2.00 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1) and two equivalent Nd(1) atoms. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Nd(1), and two equivalent Co(2) atoms to form distorted OBa2Nd2Co2 octahedra that share corners with two equivalent O(2)Ba2Nd2Co2 octahedra, corners with four equivalent O(5)Ba4Co2 octahedra, edges with two equivalent O(2)Ba2Nd2Co2 octahedra, edges with four equivalent O(4)Nd2Co2 tetrahedra, and faces with two equivalent O(5)Ba4Co2 octahedra. The corner-sharing octahedral tilt angles range from 12-61°. In the third O site, O(3) is bonded to two equivalent Mg(1) and two equivalent Co(1) atoms to form distorted OMg2Co2 trigonal pyramids that share corners with two equivalent O(5)Ba4Co2 octahedra and corners with four equivalent O(3)Mg2Co2 trigonal pyramids. The corner-sharing octahedral tilt angles are 66°. In the fourth O site, O(4) is bonded to two equivalent Nd(1) and two equivalent Co(2) atoms to form distorted ONd2Co2 tetrahedra that share corners with two equivalent O(5)Ba4Co2 octahedra, corners with four equivalent O(4)Nd2Co2 tetrahedra, and edges with four equivalent O(2)Ba2Nd2Co2 octahedra. The corner-sharing octahedral tilt angles are 64°. In the fifth O site, O(5) is bonded to four equivalent Ba(1), one Co(1), and one Co(2) atom to form OBa4Co2 octahedra that share corners with four equivalent O(2)Ba2Nd2Co2 octahedra, corners with four equivalent O(5)Ba4Co2 octahedra, corners with two equivalent O(4)Nd2Co2 tetrahedra, corners with two equivalent O(3)Mg2Co2 trigonal pyramids, edges with four equivalent O(5)Ba4Co2 octahedra, and faces with two equivalent O(2)Ba2Nd2Co2 octahedra. The corner-sharing octahedral tilt angles range from 9-61°.