Er2Zr2O7 crystallizes in the orthorhombic Pmma space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of distorted edge and corner-sharing ErO6 octahedra. The corner-sharing octahedral tilt angles are 68°. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. In the second Zr site, Zr(2) is bonded in a body-centered cubic geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(5) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Er(1) and two equivalent Zr(1) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(1)Er2Zr2 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra,  an edgeedge with one O(4)Zr4 tetrahedra, and edges with four equivalent O(2)Er3Zr tetrahedra. In the second O site, O(2) is bonded to one Er(2), two equivalent Er(1), and one Zr(1) atom to form distorted OEr3Zr tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(5)ErZr3 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with six equivalent O(2)Er3Zr tetrahedra,  an edgeedge with one O(2)Er3Zr tetrahedra,  an edgeedge with one O(5)ErZr3 tetrahedra, and edges with two equivalent O(1)Er2Zr2 tetrahedra. In the third O site, O(3) is bonded to two equivalent Er(2) and two equivalent Zr(2) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(3)Er2Zr2 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra,  an edgeedge with one O(4)Zr4 tetrahedra, and edges with four equivalent O(5)ErZr3 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Zr(1) and two equivalent Zr(2) atoms to form OZr4 tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, corners with four equivalent O(4)Zr4 tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(3)Er2Zr2 tetrahedra, and edges with four equivalent O(5)ErZr3 tetrahedra. In the fifth O site, O(5) is bonded to one Er(2), one Zr(1), and two equivalent Zr(2) atoms to form OErZr3 tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(2)Er3Zr tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with six equivalent O(5)ErZr3 tetrahedra,  an edgeedge with one O(2)Er3Zr tetrahedra,  an edgeedge with one O(5)ErZr3 tetrahedra, edges with two equivalent O(3)Er2Zr2 tetrahedra, and edges with two equivalent O(4)Zr4 tetrahedra.
Er2Zr2O7 crystallizes in the orthorhombic Pmma space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of distorted edge and corner-sharing ErO6 octahedra. The corner-sharing octahedral tilt angles are 68°. Both Er(1)-O(1) bond lengths are 2.26 Å. All Er(1)-O(2) bond lengths are 2.28 Å. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. Both Er(2)-O(2) bond lengths are 2.18 Å. Both Er(2)-O(3) bond lengths are 2.16 Å. Both Er(2)-O(5) bond lengths are 2.30 Å. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. Both Zr(1)-O(1) bond lengths are 2.30 Å. Both Zr(1)-O(2) bond lengths are 2.58 Å. Both Zr(1)-O(4) bond lengths are 2.16 Å. Both Zr(1)-O(5) bond lengths are 2.20 Å. In the second Zr site, Zr(2) is bonded in a body-centered cubic geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(5) atoms. Both Zr(2)-O(3) bond lengths are 2.23 Å. Both Zr(2)-O(4) bond lengths are 2.34 Å. All Zr(2)-O(5) bond lengths are 2.21 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Er(1) and two equivalent Zr(1) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(1)Er2Zr2 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra,  an edgeedge with one O(4)Zr4 tetrahedra, and edges with four equivalent O(2)Er3Zr tetrahedra. In the second O site, O(2) is bonded to one Er(2), two equivalent Er(1), and one Zr(1) atom to form distorted OEr3Zr tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(5)ErZr3 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with six equivalent O(2)Er3Zr tetrahedra,  an edgeedge with one O(2)Er3Zr tetrahedra,  an edgeedge with one O(5)ErZr3 tetrahedra, and edges with two equivalent O(1)Er2Zr2 tetrahedra. In the third O site, O(3) is bonded to two equivalent Er(2) and two equivalent Zr(2) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(3)Er2Zr2 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra,  an edgeedge with one O(4)Zr4 tetrahedra, and edges with four equivalent O(5)ErZr3 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Zr(1) and two equivalent Zr(2) atoms to form OZr4 tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, corners with four equivalent O(4)Zr4 tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(3)Er2Zr2 tetrahedra, and edges with four equivalent O(5)ErZr3 tetrahedra. In the fifth O site, O(5) is bonded to one Er(2), one Zr(1), and two equivalent Zr(2) atoms to form OErZr3 tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(2)Er3Zr tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with six equivalent O(5)ErZr3 tetrahedra,  an edgeedge with one O(2)Er3Zr tetrahedra,  an edgeedge with one O(5)ErZr3 tetrahedra, edges with two equivalent O(3)Er2Zr2 tetrahedra, and edges with two equivalent O(4)Zr4 tetrahedra.