BaMgYNiCuO5 crystallizes in the monoclinic Pm space group. Ba(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(5) atoms. Mg(1) is bonded in a trigonal planar geometry to one O(3) and two equivalent O(5) atoms. Y(1) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Ni(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(1) and two equivalent O(2) atoms. Cu(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(3) and two equivalent O(4) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ba(1), two equivalent Y(1), and two equivalent Ni(1) atoms to form distorted OBa2Y2Ni2 octahedra that share corners with two equivalent O(1)Ba2Y2Ni2 octahedra, corners with two equivalent O(3)Y2MgCu2 trigonal bipyramids, edges with two equivalent O(1)Ba2Y2Ni2 octahedra,  an edgeedge with one O(3)Y2MgCu2 trigonal bipyramid, and faces with four equivalent O(2)Ba2Y2Ni2 octahedra. The corner-sharing octahedral tilt angles are 2°. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Y(1), and two equivalent Ni(1) atoms to form OBa2Y2Ni2 octahedra that share corners with two equivalent O(2)Ba2Y2Ni2 octahedra, corners with four equivalent O(3)Y2MgCu2 trigonal bipyramids, edges with two equivalent O(2)Ba2Y2Ni2 octahedra, and faces with four equivalent O(1)Ba2Y2Ni2 octahedra. The corner-sharing octahedral tilt angles are 5°. In the third O site, O(3) is bonded to one Mg(1), two equivalent Y(1), and two equivalent Cu(1) atoms to form OY2MgCu2 trigonal bipyramids that share corners with two equivalent O(1)Ba2Y2Ni2 octahedra, corners with four equivalent O(2)Ba2Y2Ni2 octahedra, corners with four equivalent O(3)Y2MgCu2 trigonal bipyramids, and  an edgeedge with one O(1)Ba2Y2Ni2 octahedra. The corner-sharing octahedral tilt angles range from 4-68°. In the fourth O site, O(4) is bonded in a see-saw-like geometry to two equivalent Y(1) and two equivalent Cu(1) atoms. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to four equivalent Ba(1) and two equivalent Mg(1) atoms.
BaMgYNiCuO5 crystallizes in the monoclinic Pm space group. Ba(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(5) atoms. Both Ba(1)-O(1) bond lengths are 2.75 Å. There is one shorter (2.61 Å) and one longer (2.62 Å) Ba(1)-O(2) bond length. There are two shorter (3.30 Å) and two longer (3.37 Å) Ba(1)-O(5) bond lengths. Mg(1) is bonded in a trigonal planar geometry to one O(3) and two equivalent O(5) atoms. The Mg(1)-O(3) bond length is 1.96 Å. Both Mg(1)-O(5) bond lengths are 2.11 Å. Y(1) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Y(1)-O(1) bond lengths are 2.57 Å. There is one shorter (2.50 Å) and one longer (2.51 Å) Y(1)-O(2) bond length. Both Y(1)-O(3) bond lengths are 2.45 Å. Both Y(1)-O(4) bond lengths are 2.28 Å. Ni(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(1) and two equivalent O(2) atoms. Both Ni(1)-O(1) bond lengths are 1.89 Å. Both Ni(1)-O(2) bond lengths are 2.03 Å. Cu(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(3) and two equivalent O(4) atoms. Both Cu(1)-O(3) bond lengths are 1.89 Å. Both Cu(1)-O(4) bond lengths are 2.03 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ba(1), two equivalent Y(1), and two equivalent Ni(1) atoms to form distorted OBa2Y2Ni2 octahedra that share corners with two equivalent O(1)Ba2Y2Ni2 octahedra, corners with two equivalent O(3)Y2MgCu2 trigonal bipyramids, edges with two equivalent O(1)Ba2Y2Ni2 octahedra,  an edgeedge with one O(3)Y2MgCu2 trigonal bipyramid, and faces with four equivalent O(2)Ba2Y2Ni2 octahedra. The corner-sharing octahedral tilt angles are 2°. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Y(1), and two equivalent Ni(1) atoms to form OBa2Y2Ni2 octahedra that share corners with two equivalent O(2)Ba2Y2Ni2 octahedra, corners with four equivalent O(3)Y2MgCu2 trigonal bipyramids, edges with two equivalent O(2)Ba2Y2Ni2 octahedra, and faces with four equivalent O(1)Ba2Y2Ni2 octahedra. The corner-sharing octahedral tilt angles are 5°. In the third O site, O(3) is bonded to one Mg(1), two equivalent Y(1), and two equivalent Cu(1) atoms to form OY2MgCu2 trigonal bipyramids that share corners with two equivalent O(1)Ba2Y2Ni2 octahedra, corners with four equivalent O(2)Ba2Y2Ni2 octahedra, corners with four equivalent O(3)Y2MgCu2 trigonal bipyramids, and  an edgeedge with one O(1)Ba2Y2Ni2 octahedra. The corner-sharing octahedral tilt angles range from 4-68°. In the fourth O site, O(4) is bonded in a see-saw-like geometry to two equivalent Y(1) and two equivalent Cu(1) atoms. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to four equivalent Ba(1) and two equivalent Mg(1) atoms.