Eu2O3.MoO3 crystallizes in the monoclinic C2/c space group. There are three inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(5) atoms. In the second Eu site, Eu(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(6) atoms. In the third Eu site, Eu(3) is bonded in a 8-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms. Mo(1) is bonded in a distorted trigonal bipyramidal geometry to one O(1), one O(2), one O(3), one O(4), and one O(5) atom. There are six inequivalent O sites. In the first O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Eu(3) and one Mo(1) atom. In the second O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Eu(3) and one Mo(1) atom. In the third O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Eu(1) and one Mo(1) atom. In the fourth O site, O(6) is bonded to two equivalent Eu(2) and two equivalent Eu(3) atoms to form OEu4 tetrahedra that share corners with two equivalent O(6)Eu4 tetrahedra, corners with four equivalent O(1)Eu3Mo tetrahedra,  an edgeedge with one O(1)Eu3Mo tetrahedra, and edges with three equivalent O(6)Eu4 tetrahedra. In the fifth O site, O(1) is bonded to one Eu(1), one Eu(2), one Eu(3), and one Mo(1) atom to form OEu3Mo tetrahedra that share corners with two equivalent O(1)Eu3Mo tetrahedra, corners with four equivalent O(6)Eu4 tetrahedra, and  an edgeedge with one O(6)Eu4 tetrahedra. In the sixth O site, O(2) is bonded in a 4-coordinate geometry to one Eu(1), one Eu(2), one Eu(3), and one Mo(1) atom.
Eu2O3.MoO3 crystallizes in the monoclinic C2/c space group. There are three inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(5) atoms. Both Eu(1)-O(1) bond lengths are 2.27 Å. Both Eu(1)-O(2) bond lengths are 2.51 Å. There are two shorter (2.47 Å) and two longer (2.49 Å) Eu(1)-O(5) bond lengths. In the second Eu site, Eu(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(6) atoms. Both Eu(2)-O(1) bond lengths are 2.33 Å. Both Eu(2)-O(2) bond lengths are 2.75 Å. There are two shorter (2.32 Å) and two longer (2.40 Å) Eu(2)-O(6) bond lengths. In the third Eu site, Eu(3) is bonded in a 8-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms. The Eu(3)-O(1) bond length is 2.34 Å. The Eu(3)-O(2) bond length is 2.68 Å. There is one shorter (2.51 Å) and one longer (2.60 Å) Eu(3)-O(3) bond length. There is one shorter (2.44 Å) and one longer (2.45 Å) Eu(3)-O(4) bond length. There is one shorter (2.24 Å) and one longer (2.34 Å) Eu(3)-O(6) bond length. Mo(1) is bonded in a distorted trigonal bipyramidal geometry to one O(1), one O(2), one O(3), one O(4), and one O(5) atom. The Mo(1)-O(1) bond length is 2.19 Å. The Mo(1)-O(2) bond length is 1.81 Å. The Mo(1)-O(3) bond length is 1.79 Å. The Mo(1)-O(4) bond length is 1.83 Å. The Mo(1)-O(5) bond length is 1.78 Å. There are six inequivalent O sites. In the first O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Eu(3) and one Mo(1) atom. In the second O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Eu(3) and one Mo(1) atom. In the third O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Eu(1) and one Mo(1) atom. In the fourth O site, O(6) is bonded to two equivalent Eu(2) and two equivalent Eu(3) atoms to form OEu4 tetrahedra that share corners with two equivalent O(6)Eu4 tetrahedra, corners with four equivalent O(1)Eu3Mo tetrahedra,  an edgeedge with one O(1)Eu3Mo tetrahedra, and edges with three equivalent O(6)Eu4 tetrahedra. In the fifth O site, O(1) is bonded to one Eu(1), one Eu(2), one Eu(3), and one Mo(1) atom to form OEu3Mo tetrahedra that share corners with two equivalent O(1)Eu3Mo tetrahedra, corners with four equivalent O(6)Eu4 tetrahedra, and  an edgeedge with one O(6)Eu4 tetrahedra. In the sixth O site, O(2) is bonded in a 4-coordinate geometry to one Eu(1), one Eu(2), one Eu(3), and one Mo(1) atom.