Zr3Er4O12 crystallizes in the triclinic P-1 space group. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(8), and two equivalent O(4) atoms. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(12), one O(4), one O(6), one O(8), and one O(9) atom. In the third Er site, Er(3) is bonded to one O(10), one O(11), one O(12), one O(3), one O(6), one O(7), and one O(9) atom to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Zr(2)O6 octahedra and  an edgeedge with one Zr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the fourth Er site, Er(4) is bonded in a 7-coordinate geometry to one O(12), one O(7), one O(9), two equivalent O(11), and two equivalent O(5) atoms. There are three inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a 7-coordinate geometry to one O(1), one O(11), one O(12), one O(3), one O(5), and two equivalent O(7) atoms. In the second Zr site, Zr(2) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(9) atom to form ZrO6 octahedra that share  a cornercorner with one Er(3)O7 pentagonal bipyramid and  an edgeedge with one Er(3)O7 pentagonal bipyramid. In the third Zr site, Zr(3) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(4), one O(6), and two equivalent O(8) atoms. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Er(1), one Er(2), one Zr(1), and one Zr(2) atom to form distorted OEr2Zr2 tetrahedra that share  a cornercorner with one O(11)Er3Zr tetrahedra,  a cornercorner with one O(4)Er3Zr tetrahedra, corners with two equivalent O(7)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(10)Er3Zr tetrahedra, corners with two equivalent O(9)Er3Zr tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(6)Er2Zr2 tetrahedra,  an edgeedge with one O(12)Er3Zr tetrahedra, and  an edgeedge with one O(4)Er3Zr tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Er(1), one Zr(2), and one Zr(3) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Er(1), one Er(3), one Zr(1), and one Zr(2) atom. In the fourth O site, O(4) is bonded to one Er(2), two equivalent Er(1), and one Zr(3) atom to form distorted OEr3Zr tetrahedra that share  a cornercorner with one O(1)Er2Zr2 tetrahedra,  a cornercorner with one O(12)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(6)Er2Zr2 tetrahedra, corners with two equivalent O(10)Er3Zr tetrahedra, corners with three equivalent O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(10)Er3Zr tetrahedra, and  an edgeedge with one O(4)Er3Zr tetrahedra. In the fifth O site, O(5) is bonded to two equivalent Er(4), one Zr(1), and one Zr(2) atom to form distorted OEr2Zr2 tetrahedra that share  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(7)Er2Zr2 tetrahedra, corners with three equivalent O(11)Er3Zr tetrahedra, corners with three equivalent O(12)Er3Zr tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra, and  an edgeedge with one O(9)Er3Zr tetrahedra. In the sixth O site, O(6) is bonded to one Er(2), one Er(3), one Zr(2), and one Zr(3) atom to form distorted OEr2Zr2 tetrahedra that share  a cornercorner with one O(5)Er2Zr2 tetrahedra,  a cornercorner with one O(7)Er2Zr2 tetrahedra,  a cornercorner with one O(8)Er2Zr2 tetrahedra,  a cornercorner with one O(10)Er3Zr tetrahedra,  a cornercorner with one O(11)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(12)Er3Zr tetrahedra, corners with two equivalent O(4)Er3Zr tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(10)Er3Zr tetrahedra, and  an edgeedge with one O(9)Er3Zr tetrahedra. In the seventh O site, O(7) is bonded to one Er(3), one Er(4), and two equivalent Zr(1) atoms to form OEr2Zr2 tetrahedra that share  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(10)Er3Zr tetrahedra, corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(5)Er2Zr2 tetrahedra, corners with two equivalent O(12)Er3Zr tetrahedra, corners with two equivalent O(9)Er3Zr tetrahedra, corners with three equivalent O(11)Er3Zr tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra, and  an edgeedge with one O(12)Er3Zr tetrahedra. In the eighth O site, O(8) is bonded to one Er(1), one Er(2), and two equivalent Zr(3) atoms to form OEr2Zr2 tetrahedra that share  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(12)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(10)Er3Zr tetrahedra, corners with three equivalent O(4)Er3Zr tetrahedra,  an edgeedge with one O(6)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(10)Er3Zr tetrahedra, and  an edgeedge with one O(4)Er3Zr tetrahedra. In the ninth O site, O(9) is bonded to one Er(2), one Er(3), one Er(4), and one Zr(2) atom to form distorted OEr3Zr tetrahedra that share  a cornercorner with one O(5)Er2Zr2 tetrahedra,  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(8)Er2Zr2 tetrahedra,  a cornercorner with one O(11)Er3Zr tetrahedra,  a cornercorner with one O(12)Er3Zr tetrahedra,  a cornercorner with one O(4)Er3Zr tetrahedra, corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(7)Er2Zr2 tetrahedra, corners with two equivalent O(10)Er3Zr tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(6)Er2Zr2 tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra, and  an edgeedge with one O(12)Er3Zr tetrahedra. In the tenth O site, O(10) is bonded to one Er(1), one Er(2), one Er(3), and one Zr(3) atom to form OEr3Zr tetrahedra that share  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(7)Er2Zr2 tetrahedra,  a cornercorner with one O(11)Er3Zr tetrahedra, corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(4)Er3Zr tetrahedra, corners with two equivalent O(9)Er3Zr tetrahedra,  an edgeedge with one O(6)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(12)Er3Zr tetrahedra, and  an edgeedge with one O(4)Er3Zr tetrahedra. In the eleventh O site, O(11) is bonded to one Er(3), two equivalent Er(4), and one Zr(1) atom to form OEr3Zr tetrahedra that share  a cornercorner with one O(1)Er2Zr2 tetrahedra,  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(10)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(12)Er3Zr tetrahedra, corners with three equivalent O(5)Er2Zr2 tetrahedra, corners with three equivalent O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra,  an edgeedge with one O(12)Er3Zr tetrahedra, and  an edgeedge with one O(9)Er3Zr tetrahedra. In the twelfth O site, O(12) is bonded to one Er(2), one Er(3), one Er(4), and one Zr(1) atom to form distorted OEr3Zr tetrahedra that share  a cornercorner with one O(8)Er2Zr2 tetrahedra,  a cornercorner with one O(4)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(6)Er2Zr2 tetrahedra, corners with two equivalent O(7)Er2Zr2 tetrahedra, corners with two equivalent O(11)Er3Zr tetrahedra, corners with three equivalent O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(10)Er3Zr tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra, and  an edgeedge with one O(9)Er3Zr tetrahedra.
Zr3Er4O12 crystallizes in the triclinic P-1 space group. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(8), and two equivalent O(4) atoms. The Er(1)-O(1) bond length is 2.21 Å. The Er(1)-O(10) bond length is 2.17 Å. The Er(1)-O(2) bond length is 2.26 Å. The Er(1)-O(3) bond length is 2.61 Å. The Er(1)-O(8) bond length is 2.34 Å. There is one shorter (2.26 Å) and one longer (2.29 Å) Er(1)-O(4) bond length. In the second Er site, Er(2) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(12), one O(4), one O(6), one O(8), and one O(9) atom. The Er(2)-O(1) bond length is 2.22 Å. The Er(2)-O(10) bond length is 2.26 Å. The Er(2)-O(12) bond length is 2.26 Å. The Er(2)-O(4) bond length is 2.37 Å. The Er(2)-O(6) bond length is 2.56 Å. The Er(2)-O(8) bond length is 2.21 Å. The Er(2)-O(9) bond length is 2.22 Å. In the third Er site, Er(3) is bonded to one O(10), one O(11), one O(12), one O(3), one O(6), one O(7), and one O(9) atom to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Zr(2)O6 octahedra and  an edgeedge with one Zr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. The Er(3)-O(10) bond length is 2.25 Å. The Er(3)-O(11) bond length is 2.16 Å. The Er(3)-O(12) bond length is 2.29 Å. The Er(3)-O(3) bond length is 2.29 Å. The Er(3)-O(6) bond length is 2.29 Å. The Er(3)-O(7) bond length is 2.36 Å. The Er(3)-O(9) bond length is 2.46 Å. In the fourth Er site, Er(4) is bonded in a 7-coordinate geometry to one O(12), one O(7), one O(9), two equivalent O(11), and two equivalent O(5) atoms. The Er(4)-O(12) bond length is 2.36 Å. The Er(4)-O(7) bond length is 2.19 Å. The Er(4)-O(9) bond length is 2.23 Å. Both Er(4)-O(11) bond lengths are 2.24 Å. There is one shorter (2.25 Å) and one longer (2.58 Å) Er(4)-O(5) bond length. There are three inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a 7-coordinate geometry to one O(1), one O(11), one O(12), one O(3), one O(5), and two equivalent O(7) atoms. The Zr(1)-O(1) bond length is 2.52 Å. The Zr(1)-O(11) bond length is 2.19 Å. The Zr(1)-O(12) bond length is 2.07 Å. The Zr(1)-O(3) bond length is 2.16 Å. The Zr(1)-O(5) bond length is 2.11 Å. There is one shorter (2.15 Å) and one longer (2.22 Å) Zr(1)-O(7) bond length. In the second Zr site, Zr(2) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(9) atom to form ZrO6 octahedra that share  a cornercorner with one Er(3)O7 pentagonal bipyramid and  an edgeedge with one Er(3)O7 pentagonal bipyramid. The Zr(2)-O(1) bond length is 2.07 Å. The Zr(2)-O(2) bond length is 2.09 Å. The Zr(2)-O(3) bond length is 2.10 Å. The Zr(2)-O(5) bond length is 2.13 Å. The Zr(2)-O(6) bond length is 2.14 Å. The Zr(2)-O(9) bond length is 2.09 Å. In the third Zr site, Zr(3) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(4), one O(6), and two equivalent O(8) atoms. The Zr(3)-O(10) bond length is 2.18 Å. The Zr(3)-O(2) bond length is 2.12 Å. The Zr(3)-O(4) bond length is 2.06 Å. The Zr(3)-O(6) bond length is 2.11 Å. There is one shorter (2.10 Å) and one longer (2.21 Å) Zr(3)-O(8) bond length. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Er(1), one Er(2), one Zr(1), and one Zr(2) atom to form distorted OEr2Zr2 tetrahedra that share  a cornercorner with one O(11)Er3Zr tetrahedra,  a cornercorner with one O(4)Er3Zr tetrahedra, corners with two equivalent O(7)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(10)Er3Zr tetrahedra, corners with two equivalent O(9)Er3Zr tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(6)Er2Zr2 tetrahedra,  an edgeedge with one O(12)Er3Zr tetrahedra, and  an edgeedge with one O(4)Er3Zr tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Er(1), one Zr(2), and one Zr(3) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Er(1), one Er(3), one Zr(1), and one Zr(2) atom. In the fourth O site, O(4) is bonded to one Er(2), two equivalent Er(1), and one Zr(3) atom to form distorted OEr3Zr tetrahedra that share  a cornercorner with one O(1)Er2Zr2 tetrahedra,  a cornercorner with one O(12)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(6)Er2Zr2 tetrahedra, corners with two equivalent O(10)Er3Zr tetrahedra, corners with three equivalent O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(10)Er3Zr tetrahedra, and  an edgeedge with one O(4)Er3Zr tetrahedra. In the fifth O site, O(5) is bonded to two equivalent Er(4), one Zr(1), and one Zr(2) atom to form distorted OEr2Zr2 tetrahedra that share  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(7)Er2Zr2 tetrahedra, corners with three equivalent O(11)Er3Zr tetrahedra, corners with three equivalent O(12)Er3Zr tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra, and  an edgeedge with one O(9)Er3Zr tetrahedra. In the sixth O site, O(6) is bonded to one Er(2), one Er(3), one Zr(2), and one Zr(3) atom to form distorted OEr2Zr2 tetrahedra that share  a cornercorner with one O(5)Er2Zr2 tetrahedra,  a cornercorner with one O(7)Er2Zr2 tetrahedra,  a cornercorner with one O(8)Er2Zr2 tetrahedra,  a cornercorner with one O(10)Er3Zr tetrahedra,  a cornercorner with one O(11)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(12)Er3Zr tetrahedra, corners with two equivalent O(4)Er3Zr tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(10)Er3Zr tetrahedra, and  an edgeedge with one O(9)Er3Zr tetrahedra. In the seventh O site, O(7) is bonded to one Er(3), one Er(4), and two equivalent Zr(1) atoms to form OEr2Zr2 tetrahedra that share  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(10)Er3Zr tetrahedra, corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(5)Er2Zr2 tetrahedra, corners with two equivalent O(12)Er3Zr tetrahedra, corners with two equivalent O(9)Er3Zr tetrahedra, corners with three equivalent O(11)Er3Zr tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra, and  an edgeedge with one O(12)Er3Zr tetrahedra. In the eighth O site, O(8) is bonded to one Er(1), one Er(2), and two equivalent Zr(3) atoms to form OEr2Zr2 tetrahedra that share  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(12)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(10)Er3Zr tetrahedra, corners with three equivalent O(4)Er3Zr tetrahedra,  an edgeedge with one O(6)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(10)Er3Zr tetrahedra, and  an edgeedge with one O(4)Er3Zr tetrahedra. In the ninth O site, O(9) is bonded to one Er(2), one Er(3), one Er(4), and one Zr(2) atom to form distorted OEr3Zr tetrahedra that share  a cornercorner with one O(5)Er2Zr2 tetrahedra,  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(8)Er2Zr2 tetrahedra,  a cornercorner with one O(11)Er3Zr tetrahedra,  a cornercorner with one O(12)Er3Zr tetrahedra,  a cornercorner with one O(4)Er3Zr tetrahedra, corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(7)Er2Zr2 tetrahedra, corners with two equivalent O(10)Er3Zr tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(6)Er2Zr2 tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra, and  an edgeedge with one O(12)Er3Zr tetrahedra. In the tenth O site, O(10) is bonded to one Er(1), one Er(2), one Er(3), and one Zr(3) atom to form OEr3Zr tetrahedra that share  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(7)Er2Zr2 tetrahedra,  a cornercorner with one O(11)Er3Zr tetrahedra, corners with two equivalent O(1)Er2Zr2 tetrahedra, corners with two equivalent O(8)Er2Zr2 tetrahedra, corners with two equivalent O(4)Er3Zr tetrahedra, corners with two equivalent O(9)Er3Zr tetrahedra,  an edgeedge with one O(6)Er2Zr2 tetrahedra,  an edgeedge with one O(8)Er2Zr2 tetrahedra,  an edgeedge with one O(12)Er3Zr tetrahedra, and  an edgeedge with one O(4)Er3Zr tetrahedra. In the eleventh O site, O(11) is bonded to one Er(3), two equivalent Er(4), and one Zr(1) atom to form OEr3Zr tetrahedra that share  a cornercorner with one O(1)Er2Zr2 tetrahedra,  a cornercorner with one O(6)Er2Zr2 tetrahedra,  a cornercorner with one O(10)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(12)Er3Zr tetrahedra, corners with three equivalent O(5)Er2Zr2 tetrahedra, corners with three equivalent O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra,  an edgeedge with one O(12)Er3Zr tetrahedra, and  an edgeedge with one O(9)Er3Zr tetrahedra. In the twelfth O site, O(12) is bonded to one Er(2), one Er(3), one Er(4), and one Zr(1) atom to form distorted OEr3Zr tetrahedra that share  a cornercorner with one O(8)Er2Zr2 tetrahedra,  a cornercorner with one O(4)Er3Zr tetrahedra,  a cornercorner with one O(9)Er3Zr tetrahedra, corners with two equivalent O(6)Er2Zr2 tetrahedra, corners with two equivalent O(7)Er2Zr2 tetrahedra, corners with two equivalent O(11)Er3Zr tetrahedra, corners with three equivalent O(5)Er2Zr2 tetrahedra,  an edgeedge with one O(1)Er2Zr2 tetrahedra,  an edgeedge with one O(7)Er2Zr2 tetrahedra,  an edgeedge with one O(10)Er3Zr tetrahedra,  an edgeedge with one O(11)Er3Zr tetrahedra, and  an edgeedge with one O(9)Er3Zr tetrahedra.