LiEr6Ta2O14 crystallizes in the monoclinic C2 space group. Li(1) is bonded in a 4-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. 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(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. In the second Er site, Er(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(7) atoms. In the third Er site, Er(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms. In the fourth Er site, Er(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O6 octahedra,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-45°. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form TaO6 octahedra that share corners with two equivalent Ta(2)O6 octahedra, corners with two equivalent Er(4)O7 pentagonal bipyramids, and edges with two equivalent Er(4)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. In the second Ta site, Ta(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Er(4)O7 pentagonal bipyramids, and edges with two equivalent Er(4)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Er(1), one Er(2), one Er(3), and one Er(4) atom to form distorted OLiEr4 trigonal bipyramids that share corners with four equivalent O(7)Er4 tetrahedra,  a cornercorner with one O(1)LiEr4 trigonal bipyramid,  an edgeedge with one O(7)Er4 tetrahedra, edges with two equivalent O(5)Er3Ta tetrahedra, and  an edgeedge with one O(1)LiEr4 trigonal bipyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Li(1), one Er(1), one Er(3), one Er(4), and one Ta(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Er(1), one Er(2), one Er(4), and one Ta(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Er(1), one Er(4), one Ta(1), and one Ta(2) 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 tetrahedra that share corners with two equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(7)Er4 tetrahedra, and edges with two equivalent O(1)LiEr4 trigonal bipyramids. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Li(1), one Er(1), one Er(3), one Er(4), and one Ta(2) atom. In the seventh O site, O(7) is bonded to one Er(1), one Er(2), one Er(3), and one Er(4) atom to form OEr4 tetrahedra that share corners with two equivalent O(7)Er4 tetrahedra, corners with four equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(1)LiEr4 trigonal bipyramids, and  an edgeedge with one O(1)LiEr4 trigonal bipyramid.
LiEr6Ta2O14 crystallizes in the monoclinic C2 space group. Li(1) is bonded in a 4-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. Both Li(1)-O(1) bond lengths are 1.98 Å. Both Li(1)-O(2) bond lengths are 1.96 Å. Both Li(1)-O(6) bond lengths are 2.54 Å. 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(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. The Er(1)-O(1) bond length is 2.26 Å. The Er(1)-O(2) bond length is 2.44 Å. The Er(1)-O(3) bond length is 2.29 Å. The Er(1)-O(4) bond length is 2.68 Å. The Er(1)-O(5) bond length is 2.23 Å. The Er(1)-O(6) bond length is 2.34 Å. The Er(1)-O(7) bond length is 2.19 Å. In the second Er site, Er(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(7) atoms. Both Er(2)-O(1) bond lengths are 2.54 Å. Both Er(2)-O(3) bond lengths are 2.67 Å. Both Er(2)-O(5) bond lengths are 2.46 Å. Both Er(2)-O(7) bond lengths are 2.31 Å. In the third Er site, Er(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms. Both Er(3)-O(1) bond lengths are 2.40 Å. Both Er(3)-O(2) bond lengths are 2.57 Å. Both Er(3)-O(6) bond lengths are 2.75 Å. Both Er(3)-O(7) bond lengths are 2.27 Å. In the fourth Er site, Er(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O6 octahedra,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-45°. The Er(4)-O(1) bond length is 2.18 Å. The Er(4)-O(2) bond length is 2.34 Å. The Er(4)-O(3) bond length is 2.28 Å. The Er(4)-O(4) bond length is 2.50 Å. The Er(4)-O(5) bond length is 2.34 Å. The Er(4)-O(6) bond length is 2.45 Å. The Er(4)-O(7) bond length is 2.27 Å. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form TaO6 octahedra that share corners with two equivalent Ta(2)O6 octahedra, corners with two equivalent Er(4)O7 pentagonal bipyramids, and edges with two equivalent Er(4)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. Both Ta(1)-O(3) bond lengths are 2.02 Å. Both Ta(1)-O(4) bond lengths are 1.98 Å. Both Ta(1)-O(5) bond lengths are 2.07 Å. In the second Ta site, Ta(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Er(4)O7 pentagonal bipyramids, and edges with two equivalent Er(4)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. Both Ta(2)-O(2) bond lengths are 2.09 Å. Both Ta(2)-O(4) bond lengths are 1.98 Å. Both Ta(2)-O(6) bond lengths are 1.96 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Er(1), one Er(2), one Er(3), and one Er(4) atom to form distorted OLiEr4 trigonal bipyramids that share corners with four equivalent O(7)Er4 tetrahedra,  a cornercorner with one O(1)LiEr4 trigonal bipyramid,  an edgeedge with one O(7)Er4 tetrahedra, edges with two equivalent O(5)Er3Ta tetrahedra, and  an edgeedge with one O(1)LiEr4 trigonal bipyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Li(1), one Er(1), one Er(3), one Er(4), and one Ta(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Er(1), one Er(2), one Er(4), and one Ta(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Er(1), one Er(4), one Ta(1), and one Ta(2) 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 tetrahedra that share corners with two equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(7)Er4 tetrahedra, and edges with two equivalent O(1)LiEr4 trigonal bipyramids. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Li(1), one Er(1), one Er(3), one Er(4), and one Ta(2) atom. In the seventh O site, O(7) is bonded to one Er(1), one Er(2), one Er(3), and one Er(4) atom to form OEr4 tetrahedra that share corners with two equivalent O(7)Er4 tetrahedra, corners with four equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(1)LiEr4 trigonal bipyramids, and  an edgeedge with one O(1)LiEr4 trigonal bipyramid.