CaEr4Zr4O14 crystallizes in the monoclinic Pm space group. Ca(1) is bonded to one O(10) and four equivalent O(9) atoms to form distorted edge-sharing CaO5 square pyramids. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to one O(1), one O(10), two equivalent O(2), and two equivalent O(9) atoms. 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(6) atoms. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to two equivalent O(5), two equivalent O(8), and two equivalent O(9) atoms. There are three inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(5), two equivalent O(7), and two equivalent O(9) atoms. In the second Zr site, Zr(2) is bonded in a 8-coordinate geometry to two equivalent O(10), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms. In the third Zr site, Zr(3) is bonded in a 7-coordinate geometry to one O(3), one O(7), one O(8), two equivalent O(5), and two equivalent O(6) atoms. There are ten 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(1)Er2Zr2 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, and  an edgeedge with one O(7)Zr4 tetrahedra. In the second O site, O(2) is bonded to one Er(2), two equivalent Er(1), and one Zr(2) atom to form OEr3Zr tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, and corners with four equivalent O(2)Er3Zr tetrahedra. In the third O site, O(3) is bonded to two equivalent Er(2) and two equivalent Zr(3) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, and  an edgeedge with one O(7)Zr4 tetrahedra. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Zr(2) atoms. In the fifth O site, O(5) is bonded to one Er(3), one Zr(1), and two equivalent Zr(3) atoms to form distorted OErZr3 tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, edges with two equivalent O(8)Er2Zr2 tetrahedra, and edges with two equivalent O(7)Zr4 tetrahedra. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Er(2), one Zr(2), and two equivalent Zr(3) atoms. In the seventh O site, O(7) is bonded to two equivalent Zr(1) and two equivalent Zr(3) atoms to form OZr4 tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(7)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 eighth O site, O(8) is bonded to two equivalent Er(3) and two equivalent Zr(3) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, and edges with four equivalent O(5)ErZr3 tetrahedra. In the ninth O site, O(9) is bonded in a 6-coordinate geometry to two equivalent Ca(1), one Er(3), two equivalent Er(1), and one Zr(1) atom. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Er(1), and two equivalent Zr(2) atoms.
CaEr4Zr4O14 crystallizes in the monoclinic Pm space group. Ca(1) is bonded to one O(10) and four equivalent O(9) atoms to form distorted edge-sharing CaO5 square pyramids. The Ca(1)-O(10) bond length is 2.11 Å. There are two shorter (2.32 Å) and two longer (2.33 Å) Ca(1)-O(9) bond lengths. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to one O(1), one O(10), two equivalent O(2), and two equivalent O(9) atoms. The Er(1)-O(1) bond length is 2.40 Å. The Er(1)-O(10) bond length is 2.38 Å. There is one shorter (2.24 Å) and one longer (2.25 Å) Er(1)-O(2) bond length. There is one shorter (2.53 Å) and one longer (2.58 Å) Er(1)-O(9) bond length. 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(6) atoms. Both Er(2)-O(2) bond lengths are 2.26 Å. Both Er(2)-O(3) bond lengths are 2.21 Å. Both Er(2)-O(6) bond lengths are 2.50 Å. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to two equivalent O(5), two equivalent O(8), and two equivalent O(9) atoms. Both Er(3)-O(5) bond lengths are 2.20 Å. Both Er(3)-O(8) bond lengths are 2.12 Å. Both Er(3)-O(9) bond lengths are 2.50 Å. There are three inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(5), two equivalent O(7), and two equivalent O(9) atoms. There is one shorter (2.25 Å) and one longer (2.26 Å) Zr(1)-O(1) bond length. Both Zr(1)-O(5) bond lengths are 2.12 Å. Both Zr(1)-O(7) bond lengths are 2.25 Å. Both Zr(1)-O(9) bond lengths are 2.86 Å. In the second Zr site, Zr(2) is bonded in a 8-coordinate geometry to two equivalent O(10), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms. There is one shorter (2.38 Å) and one longer (2.39 Å) Zr(2)-O(10) bond length. Both Zr(2)-O(2) bond lengths are 2.22 Å. There is one shorter (2.07 Å) and one longer (2.08 Å) Zr(2)-O(4) bond length. Both Zr(2)-O(6) bond lengths are 2.59 Å. In the third Zr site, Zr(3) is bonded in a 7-coordinate geometry to one O(3), one O(7), one O(8), two equivalent O(5), and two equivalent O(6) atoms. The Zr(3)-O(3) bond length is 2.16 Å. The Zr(3)-O(7) bond length is 2.20 Å. The Zr(3)-O(8) bond length is 2.35 Å. Both Zr(3)-O(5) bond lengths are 2.35 Å. Both Zr(3)-O(6) bond lengths are 2.09 Å. There are ten 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(1)Er2Zr2 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, and  an edgeedge with one O(7)Zr4 tetrahedra. In the second O site, O(2) is bonded to one Er(2), two equivalent Er(1), and one Zr(2) atom to form OEr3Zr tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, and corners with four equivalent O(2)Er3Zr tetrahedra. In the third O site, O(3) is bonded to two equivalent Er(2) and two equivalent Zr(3) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with four equivalent O(2)Er3Zr tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, and  an edgeedge with one O(7)Zr4 tetrahedra. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Zr(2) atoms. In the fifth O site, O(5) is bonded to one Er(3), one Zr(1), and two equivalent Zr(3) atoms to form distorted OErZr3 tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, edges with two equivalent O(8)Er2Zr2 tetrahedra, and edges with two equivalent O(7)Zr4 tetrahedra. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Er(2), one Zr(2), and two equivalent Zr(3) atoms. In the seventh O site, O(7) is bonded to two equivalent Zr(1) and two equivalent Zr(3) atoms to form OZr4 tetrahedra that share corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(7)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 eighth O site, O(8) is bonded to two equivalent Er(3) and two equivalent Zr(3) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, and edges with four equivalent O(5)ErZr3 tetrahedra. In the ninth O site, O(9) is bonded in a 6-coordinate geometry to two equivalent Ca(1), one Er(3), two equivalent Er(1), and one Zr(1) atom. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Er(1), and two equivalent Zr(2) atoms.