CaEr4Zr4O14 crystallizes in the monoclinic Pm space group. Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(9) atoms. 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 body-centered cubic 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 body-centered cubic geometry to one O(3), one O(4), 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 in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Er(1), and two equivalent Zr(1) atoms. In the second O site, O(2) is bonded to one Ca(1), one Er(2), two equivalent Er(1), and one Zr(2) atom to form distorted OCaEr3Zr trigonal bipyramids that share corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(6)ErZr3 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with three equivalent O(2)CaEr3Zr trigonal bipyramids,  an edgeedge with one O(6)ErZr3 tetrahedra, edges with two equivalent O(10)Er2Zr2 tetrahedra, and  an edgeedge with one O(2)CaEr3Zr trigonal bipyramid. 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 two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, corners with four equivalent O(2)CaEr3Zr trigonal bipyramids,  an edgeedge with one O(7)Zr4 tetrahedra, and edges with four equivalent O(6)ErZr3 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Zr(2) and two equivalent Zr(3) atoms to form OZr4 tetrahedra that share corners with two equivalent O(10)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, corners with four equivalent O(2)CaEr3Zr trigonal bipyramids,  an edgeedge with one O(10)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra, and edges with four equivalent O(6)ErZr3 tetrahedra. In the fifth O site, O(5) is bonded to one Er(3), one Zr(1), and two equivalent Zr(3) atoms to form OErZr3 tetrahedra that share corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(6)ErZr3 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra,  an edgeedge with one O(6)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 to one Er(2), one Zr(2), and two equivalent Zr(3) atoms to form OErZr3 tetrahedra that share corners with two equivalent O(10)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(5)ErZr3 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, corners with four equivalent O(6)ErZr3 tetrahedra, corners with two equivalent O(2)CaEr3Zr trigonal bipyramids,  an edgeedge with one O(5)ErZr3 tetrahedra, edges with two equivalent O(3)Er2Zr2 tetrahedra, edges with two equivalent O(4)Zr4 tetrahedra, and  an edgeedge with one O(2)CaEr3Zr trigonal bipyramid. 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(8)Er2Zr2 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, corners with four equivalent O(6)ErZr3 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, corners with four equivalent O(6)ErZr3 tetrahedra,  an edgeedge with one O(4)Zr4 tetrahedra, and edges with four equivalent O(5)ErZr3 tetrahedra. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one Ca(1), one Er(3), two equivalent Er(1), and one Zr(1) atom. In the tenth O site, O(10) is bonded to two equivalent Er(1) and two equivalent Zr(2) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(10)Er2Zr2 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(6)ErZr3 tetrahedra,  an edgeedge with one O(4)Zr4 tetrahedra, and edges with four equivalent O(2)CaEr3Zr trigonal bipyramids.
CaEr4Zr4O14 crystallizes in the monoclinic Pm space group. Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(9) atoms. Both Ca(1)-O(1) bond lengths are 2.26 Å. Both Ca(1)-O(2) bond lengths are 2.24 Å. Both Ca(1)-O(9) bond lengths are 2.43 Å. 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 2.59 Å. The Er(1)-O(10) bond length is 2.23 Å. There is one shorter (2.46 Å) and one longer (2.47 Å) Er(1)-O(2) bond length. Both Er(1)-O(9) bond lengths are 2.24 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(6) atoms. Both Er(2)-O(2) bond lengths are 2.30 Å. Both Er(2)-O(3) bond lengths are 2.16 Å. Both Er(2)-O(6) bond lengths are 2.32 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 2.41 Å. Both Er(3)-O(8) bond lengths are 2.28 Å. Both Er(3)-O(9) bond lengths are 2.23 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 (2.44 Å) and one longer (2.48 Å) Zr(1)-O(1) bond length. Both Zr(1)-O(5) bond lengths are 2.10 Å. There is one shorter (2.11 Å) and one longer (2.13 Å) Zr(1)-O(7) bond length. Both Zr(1)-O(9) bond lengths are 2.65 Å. In the second Zr site, Zr(2) is bonded in a body-centered cubic geometry to two equivalent O(10), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms. Both Zr(2)-O(10) bond lengths are 2.25 Å. Both Zr(2)-O(2) bond lengths are 2.54 Å. Both Zr(2)-O(4) bond lengths are 2.24 Å. Both Zr(2)-O(6) bond lengths are 2.18 Å. In the third Zr site, Zr(3) is bonded in a body-centered cubic geometry to one O(3), one O(4), one O(7), one O(8), two equivalent O(5), and two equivalent O(6) atoms. The Zr(3)-O(3) bond length is 2.34 Å. The Zr(3)-O(4) bond length is 2.22 Å. The Zr(3)-O(7) bond length is 2.40 Å. The Zr(3)-O(8) bond length is 2.20 Å. Both Zr(3)-O(5) bond lengths are 2.25 Å. There is one shorter (2.23 Å) and one longer (2.24 Å) Zr(3)-O(6) bond length. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Er(1), and two equivalent Zr(1) atoms. In the second O site, O(2) is bonded to one Ca(1), one Er(2), two equivalent Er(1), and one Zr(2) atom to form distorted OCaEr3Zr trigonal bipyramids that share corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(6)ErZr3 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with three equivalent O(2)CaEr3Zr trigonal bipyramids,  an edgeedge with one O(6)ErZr3 tetrahedra, edges with two equivalent O(10)Er2Zr2 tetrahedra, and  an edgeedge with one O(2)CaEr3Zr trigonal bipyramid. 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 two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, corners with four equivalent O(2)CaEr3Zr trigonal bipyramids,  an edgeedge with one O(7)Zr4 tetrahedra, and edges with four equivalent O(6)ErZr3 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Zr(2) and two equivalent Zr(3) atoms to form OZr4 tetrahedra that share corners with two equivalent O(10)Er2Zr2 tetrahedra, corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra, corners with four equivalent O(2)CaEr3Zr trigonal bipyramids,  an edgeedge with one O(10)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra, and edges with four equivalent O(6)ErZr3 tetrahedra. In the fifth O site, O(5) is bonded to one Er(3), one Zr(1), and two equivalent Zr(3) atoms to form OErZr3 tetrahedra that share corners with two equivalent O(3)Er2Zr2 tetrahedra, corners with two equivalent O(6)ErZr3 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(5)ErZr3 tetrahedra,  an edgeedge with one O(6)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 to one Er(2), one Zr(2), and two equivalent Zr(3) atoms to form OErZr3 tetrahedra that share corners with two equivalent O(10)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(5)ErZr3 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, corners with four equivalent O(6)ErZr3 tetrahedra, corners with two equivalent O(2)CaEr3Zr trigonal bipyramids,  an edgeedge with one O(5)ErZr3 tetrahedra, edges with two equivalent O(3)Er2Zr2 tetrahedra, edges with two equivalent O(4)Zr4 tetrahedra, and  an edgeedge with one O(2)CaEr3Zr trigonal bipyramid. 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(8)Er2Zr2 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with two equivalent O(7)Zr4 tetrahedra, corners with four equivalent O(6)ErZr3 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, corners with four equivalent O(6)ErZr3 tetrahedra,  an edgeedge with one O(4)Zr4 tetrahedra, and edges with four equivalent O(5)ErZr3 tetrahedra. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one Ca(1), one Er(3), two equivalent Er(1), and one Zr(1) atom. In the tenth O site, O(10) is bonded to two equivalent Er(1) and two equivalent Zr(2) atoms to form OEr2Zr2 tetrahedra that share corners with two equivalent O(10)Er2Zr2 tetrahedra, corners with two equivalent O(4)Zr4 tetrahedra, corners with four equivalent O(6)ErZr3 tetrahedra,  an edgeedge with one O(4)Zr4 tetrahedra, and edges with four equivalent O(2)CaEr3Zr trigonal bipyramids.