LiEr6Ta2O14 crystallizes in the monoclinic Cm space group. Li(1) is bonded in a distorted trigonal planar geometry to one O(7) and two equivalent O(2) atoms. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), and two equivalent O(2) atoms. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. In the fourth Er site, Er(4) is bonded in a 7-coordinate geometry to one O(3), one O(4), one O(5), one O(6), one O(8), and two equivalent O(1) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(7), one O(8), two equivalent O(4), and two equivalent O(5) atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 30-68°. In the second Ta site, Ta(2) is bonded to one O(7), one O(8), two equivalent O(3), and two equivalent O(6) atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 30-68°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Er(2), one Er(3), and two equivalent Er(4) atoms to form OEr4 tetrahedra that share corners with two equivalent O(1)Er4 tetrahedra, corners with two equivalent O(5)Er3Ta trigonal pyramids, corners with two equivalent O(6)Er3Ta trigonal pyramids,  an edgeedge with one O(1)Er4 tetrahedra,  an edgeedge with one O(5)Er3Ta trigonal pyramid, and  an edgeedge with one O(6)Er3Ta trigonal pyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Li(1), one Er(2), one Er(3), and two equivalent Er(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Er(1), one Er(4), and one Ta(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Er(1), one Er(4), and one Ta(1) atom. In the fifth O site, O(5) is bonded to one Er(1), one Er(2), one Er(4), and one Ta(1) atom to form distorted OEr3Ta trigonal pyramids that share corners with two equivalent O(1)Er4 tetrahedra, corners with two equivalent O(6)Er3Ta trigonal pyramids,  an edgeedge with one O(1)Er4 tetrahedra, and  an edgeedge with one O(5)Er3Ta trigonal pyramid. In the sixth O site, O(6) is bonded to one Er(1), one Er(3), one Er(4), and one Ta(2) atom to form distorted OEr3Ta trigonal pyramids that share corners with two equivalent O(1)Er4 tetrahedra, corners with two equivalent O(5)Er3Ta trigonal pyramids,  an edgeedge with one O(1)Er4 tetrahedra, and  an edgeedge with one O(6)Er3Ta trigonal pyramid. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Li(1), one Ta(1), and one Ta(2) atom. In the eighth O site, O(8) is bonded in a distorted water-like geometry to two equivalent Er(4), one Ta(1), and one Ta(2) atom.
LiEr6Ta2O14 crystallizes in the monoclinic Cm space group. Li(1) is bonded in a distorted trigonal planar geometry to one O(7) and two equivalent O(2) atoms. The Li(1)-O(7) bond length is 1.82 Å. Both Li(1)-O(2) bond lengths are 1.86 Å. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), and two equivalent O(2) atoms. The Er(1)-O(3) bond length is 2.36 Å. The Er(1)-O(4) bond length is 2.36 Å. The Er(1)-O(5) bond length is 2.23 Å. The Er(1)-O(6) bond length is 2.21 Å. There is one shorter (2.27 Å) and one longer (2.37 Å) Er(1)-O(2) bond length. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms. Both Er(2)-O(1) bond lengths are 2.27 Å. Both Er(2)-O(2) bond lengths are 2.52 Å. Both Er(2)-O(5) bond lengths are 2.24 Å. In the third Er site, Er(3) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. Both Er(3)-O(1) bond lengths are 2.29 Å. Both Er(3)-O(2) bond lengths are 2.46 Å. Both Er(3)-O(6) bond lengths are 2.25 Å. In the fourth Er site, Er(4) is bonded in a 7-coordinate geometry to one O(3), one O(4), one O(5), one O(6), one O(8), and two equivalent O(1) atoms. The Er(4)-O(3) bond length is 2.21 Å. The Er(4)-O(4) bond length is 2.23 Å. The Er(4)-O(5) bond length is 2.40 Å. The Er(4)-O(6) bond length is 2.41 Å. The Er(4)-O(8) bond length is 2.65 Å. There is one shorter (2.27 Å) and one longer (2.31 Å) Er(4)-O(1) bond length. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(7), one O(8), two equivalent O(4), and two equivalent O(5) atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 30-68°. The Ta(1)-O(7) bond length is 2.02 Å. The Ta(1)-O(8) bond length is 2.01 Å. Both Ta(1)-O(4) bond lengths are 1.95 Å. Both Ta(1)-O(5) bond lengths are 2.12 Å. In the second Ta site, Ta(2) is bonded to one O(7), one O(8), two equivalent O(3), and two equivalent O(6) atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles range from 30-68°. The Ta(2)-O(7) bond length is 2.01 Å. The Ta(2)-O(8) bond length is 2.03 Å. Both Ta(2)-O(3) bond lengths are 1.95 Å. Both Ta(2)-O(6) bond lengths are 2.12 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Er(2), one Er(3), and two equivalent Er(4) atoms to form OEr4 tetrahedra that share corners with two equivalent O(1)Er4 tetrahedra, corners with two equivalent O(5)Er3Ta trigonal pyramids, corners with two equivalent O(6)Er3Ta trigonal pyramids,  an edgeedge with one O(1)Er4 tetrahedra,  an edgeedge with one O(5)Er3Ta trigonal pyramid, and  an edgeedge with one O(6)Er3Ta trigonal pyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Li(1), one Er(2), one Er(3), and two equivalent Er(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Er(1), one Er(4), and one Ta(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Er(1), one Er(4), and one Ta(1) atom. In the fifth O site, O(5) is bonded to one Er(1), one Er(2), one Er(4), and one Ta(1) atom to form distorted OEr3Ta trigonal pyramids that share corners with two equivalent O(1)Er4 tetrahedra, corners with two equivalent O(6)Er3Ta trigonal pyramids,  an edgeedge with one O(1)Er4 tetrahedra, and  an edgeedge with one O(5)Er3Ta trigonal pyramid. In the sixth O site, O(6) is bonded to one Er(1), one Er(3), one Er(4), and one Ta(2) atom to form distorted OEr3Ta trigonal pyramids that share corners with two equivalent O(1)Er4 tetrahedra, corners with two equivalent O(5)Er3Ta trigonal pyramids,  an edgeedge with one O(1)Er4 tetrahedra, and  an edgeedge with one O(6)Er3Ta trigonal pyramid. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Li(1), one Ta(1), and one Ta(2) atom. In the eighth O site, O(8) is bonded in a distorted water-like geometry to two equivalent Er(4), one Ta(1), and one Ta(2) atom.