BaEr2ZnO5 crystallizes in the orthorhombic Pnma space group. Ba(1) is bonded in a 11-coordinate geometry to three equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(1), two equivalent O(2), and four equivalent O(3) atoms to form distorted ErO7 pentagonal bipyramids that share corners with five equivalent Zn(1)O5 trigonal bipyramids, edges with two equivalent Er(1)O7 pentagonal bipyramids, and  an edgeedge with one Zn(1)O5 trigonal bipyramid. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(3), and four equivalent O(2) atoms. Zn(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted ZnO5 trigonal bipyramids that share corners with five equivalent Er(1)O7 pentagonal bipyramids and  an edgeedge with one Er(1)O7 pentagonal bipyramid. There are three inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ba(1), one Er(1), one Er(2), and one Zn(1) atom to form distorted OBa3Er2Zn octahedra that share corners with two equivalent O(1)Ba3Er2Zn octahedra, corners with eight equivalent O(2)Ba2Er3Zn octahedra, edges with two equivalent O(1)Ba3Er2Zn octahedra, and faces with four equivalent O(2)Ba2Er3Zn octahedra. The corner-sharing octahedral tilt angles range from 0-64°. In the second O site, O(2) is bonded to two equivalent Ba(1), one Er(1), two equivalent Er(2), and one Zn(1) atom to form distorted OBa2Er3Zn octahedra that share corners with four equivalent O(2)Ba2Er3Zn octahedra, corners with four equivalent O(1)Ba3Er2Zn octahedra, edges with two equivalent O(2)Ba2Er3Zn octahedra, faces with two equivalent O(2)Ba2Er3Zn octahedra, and faces with two equivalent O(1)Ba3Er2Zn octahedra. The corner-sharing octahedral tilt angles range from 26-77°. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Er(2), two equivalent Er(1), and one Zn(1) atom.
BaEr2ZnO5 crystallizes in the orthorhombic Pnma space group. Ba(1) is bonded in a 11-coordinate geometry to three equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms. There is one shorter (2.74 Å) and two longer (2.86 Å) Ba(1)-O(1) bond lengths. There are two shorter (2.89 Å) and two longer (3.01 Å) Ba(1)-O(2) bond lengths. There are two shorter (3.12 Å) and two longer (3.31 Å) Ba(1)-O(3) bond lengths. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(1), two equivalent O(2), and four equivalent O(3) atoms to form distorted ErO7 pentagonal bipyramids that share corners with five equivalent Zn(1)O5 trigonal bipyramids, edges with two equivalent Er(1)O7 pentagonal bipyramids, and  an edgeedge with one Zn(1)O5 trigonal bipyramid. The Er(1)-O(1) bond length is 2.31 Å. Both Er(1)-O(2) bond lengths are 2.36 Å. There are two shorter (2.29 Å) and two longer (2.35 Å) Er(1)-O(3) bond lengths. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to one O(1), two equivalent O(3), and four equivalent O(2) atoms. The Er(2)-O(1) bond length is 2.37 Å. Both Er(2)-O(3) bond lengths are 2.29 Å. There are two shorter (2.34 Å) and two longer (2.38 Å) Er(2)-O(2) bond lengths. Zn(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted ZnO5 trigonal bipyramids that share corners with five equivalent Er(1)O7 pentagonal bipyramids and  an edgeedge with one Er(1)O7 pentagonal bipyramid. The Zn(1)-O(1) bond length is 2.00 Å. Both Zn(1)-O(2) bond lengths are 2.14 Å. Both Zn(1)-O(3) bond lengths are 2.05 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ba(1), one Er(1), one Er(2), and one Zn(1) atom to form distorted OBa3Er2Zn octahedra that share corners with two equivalent O(1)Ba3Er2Zn octahedra, corners with eight equivalent O(2)Ba2Er3Zn octahedra, edges with two equivalent O(1)Ba3Er2Zn octahedra, and faces with four equivalent O(2)Ba2Er3Zn octahedra. The corner-sharing octahedral tilt angles range from 0-64°. In the second O site, O(2) is bonded to two equivalent Ba(1), one Er(1), two equivalent Er(2), and one Zn(1) atom to form distorted OBa2Er3Zn octahedra that share corners with four equivalent O(2)Ba2Er3Zn octahedra, corners with four equivalent O(1)Ba3Er2Zn octahedra, edges with two equivalent O(2)Ba2Er3Zn octahedra, faces with two equivalent O(2)Ba2Er3Zn octahedra, and faces with two equivalent O(1)Ba3Er2Zn octahedra. The corner-sharing octahedral tilt angles range from 26-77°. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Er(2), two equivalent Er(1), and one Zn(1) atom.