BaMgYNiCuO5 crystallizes in the orthorhombic Pmm2 space group. Ba(1) is bonded in a 8-coordinate geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(5) atoms. Mg(1) is bonded in a trigonal planar geometry to one O(1) and two equivalent O(5) atoms. Y(1) is bonded in a distorted 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 one Mg(1), two equivalent Y(1), and two equivalent Ni(1) atoms to form OY2MgNi2 trigonal bipyramids that share corners with two equivalent O(3)Ba2Y2Cu2 octahedra, corners with four equivalent O(4)Ba2Y2Cu2 octahedra, corners with four equivalent O(1)Y2MgNi2 trigonal bipyramids, and  an edgeedge with one O(3)Ba2Y2Cu2 octahedra. The corner-sharing octahedral tilt angles range from 9-70°. In the second O site, O(2) is bonded in a see-saw-like geometry to two equivalent Y(1) and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded to two equivalent Ba(1), two equivalent Y(1), and two equivalent Cu(1) atoms to form distorted OBa2Y2Cu2 octahedra that share corners with two equivalent O(3)Ba2Y2Cu2 octahedra, corners with two equivalent O(1)Y2MgNi2 trigonal bipyramids, edges with two equivalent O(3)Ba2Y2Cu2 octahedra,  an edgeedge with one O(1)Y2MgNi2 trigonal bipyramid, and faces with four equivalent O(4)Ba2Y2Cu2 octahedra. The corner-sharing octahedral tilt angles are 9°. In the fourth O site, O(4) is bonded to two equivalent Ba(1), two equivalent Y(1), and two equivalent Cu(1) atoms to form OBa2Y2Cu2 octahedra that share corners with two equivalent O(4)Ba2Y2Cu2 octahedra, corners with four equivalent O(1)Y2MgNi2 trigonal bipyramids, edges with two equivalent O(4)Ba2Y2Cu2 octahedra, and faces with four equivalent O(3)Ba2Y2Cu2 octahedra. The corner-sharing octahedral tilt angles are 5°. 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 orthorhombic Pmm2 space group. Ba(1) is bonded in a 8-coordinate geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(5) atoms. Both Ba(1)-O(3) bond lengths are 2.72 Å. Both Ba(1)-O(4) bond lengths are 2.64 Å. All Ba(1)-O(5) bond lengths are 3.27 Å. Mg(1) is bonded in a trigonal planar geometry to one O(1) and two equivalent O(5) atoms. The Mg(1)-O(1) bond length is 1.96 Å. Both Mg(1)-O(5) bond lengths are 2.12 Å. Y(1) is bonded in a distorted 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 2.40 Å. Both Y(1)-O(2) bond lengths are 2.25 Å. Both Y(1)-O(3) bond lengths are 2.68 Å. Both Y(1)-O(4) bond lengths are 2.52 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 1.88 Å. Both Ni(1)-O(2) bond lengths are 2.05 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 2.05 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), two equivalent Y(1), and two equivalent Ni(1) atoms to form OY2MgNi2 trigonal bipyramids that share corners with two equivalent O(3)Ba2Y2Cu2 octahedra, corners with four equivalent O(4)Ba2Y2Cu2 octahedra, corners with four equivalent O(1)Y2MgNi2 trigonal bipyramids, and  an edgeedge with one O(3)Ba2Y2Cu2 octahedra. The corner-sharing octahedral tilt angles range from 9-70°. In the second O site, O(2) is bonded in a see-saw-like geometry to two equivalent Y(1) and two equivalent Ni(1) atoms. In the third O site, O(3) is bonded to two equivalent Ba(1), two equivalent Y(1), and two equivalent Cu(1) atoms to form distorted OBa2Y2Cu2 octahedra that share corners with two equivalent O(3)Ba2Y2Cu2 octahedra, corners with two equivalent O(1)Y2MgNi2 trigonal bipyramids, edges with two equivalent O(3)Ba2Y2Cu2 octahedra,  an edgeedge with one O(1)Y2MgNi2 trigonal bipyramid, and faces with four equivalent O(4)Ba2Y2Cu2 octahedra. The corner-sharing octahedral tilt angles are 9°. In the fourth O site, O(4) is bonded to two equivalent Ba(1), two equivalent Y(1), and two equivalent Cu(1) atoms to form OBa2Y2Cu2 octahedra that share corners with two equivalent O(4)Ba2Y2Cu2 octahedra, corners with four equivalent O(1)Y2MgNi2 trigonal bipyramids, edges with two equivalent O(4)Ba2Y2Cu2 octahedra, and faces with four equivalent O(3)Ba2Y2Cu2 octahedra. The corner-sharing octahedral tilt angles are 5°. 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.