Er2EuO4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(3), two equivalent O(4), and three equivalent O(2) atoms to form a mixture of corner and edge-sharing ErO6 octahedra. The corner-sharing octahedral tilt angles range from 50-64°. In the second Er site, Er(2) is bonded to one O(4), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing ErO6 octahedra. The corner-sharing octahedral tilt angles range from 50-64°. Eu(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Er(2) and two equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing OEu2Er3 trigonal bipyramids. In the second O site, O(2) is bonded to three equivalent Er(1) and two equivalent Eu(1) atoms to form a mixture of corner and edge-sharing OEu2Er3 square pyramids. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Er(1), two equivalent Er(2), and two equivalent Eu(1) atoms. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Er(2), two equivalent Er(1), and two equivalent Eu(1) atoms.
Er2EuO4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one O(3), two equivalent O(4), and three equivalent O(2) atoms to form a mixture of corner and edge-sharing ErO6 octahedra. The corner-sharing octahedral tilt angles range from 50-64°. The Er(1)-O(3) bond length is 2.24 Å. Both Er(1)-O(4) bond lengths are 2.20 Å. There is one shorter (2.29 Å) and two longer (2.35 Å) Er(1)-O(2) bond lengths. In the second Er site, Er(2) is bonded to one O(4), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing ErO6 octahedra. The corner-sharing octahedral tilt angles range from 50-64°. The Er(2)-O(4) bond length is 2.24 Å. Both Er(2)-O(3) bond lengths are 2.28 Å. There is one shorter (2.25 Å) and two longer (2.32 Å) Er(2)-O(1) bond lengths. Eu(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Eu(1)-O(1) bond lengths are 2.58 Å. Both Eu(1)-O(2) bond lengths are 2.58 Å. Both Eu(1)-O(3) bond lengths are 2.72 Å. There is one shorter (2.74 Å) and one longer (2.86 Å) Eu(1)-O(4) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Er(2) and two equivalent Eu(1) atoms to form a mixture of distorted corner and edge-sharing OEu2Er3 trigonal bipyramids. In the second O site, O(2) is bonded to three equivalent Er(1) and two equivalent Eu(1) atoms to form a mixture of corner and edge-sharing OEu2Er3 square pyramids. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Er(1), two equivalent Er(2), and two equivalent Eu(1) atoms. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Er(2), two equivalent Er(1), and two equivalent Eu(1) atoms.