NaEr(SO4)2 crystallizes in the monoclinic P2_1/m space group. Na(1) is bonded in a 7-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms. Er(1) is bonded in a 8-coordinate geometry to one O(2), one O(4), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. There are two inequivalent S sites. In the first S site, S(1) is bonded in a tetrahedral geometry to one O(4), one O(5), and two equivalent O(3) atoms. In the second S site, S(2) is bonded in a tetrahedral geometry to one O(1), one O(2), and two equivalent O(6) atoms. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one S(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Er(1), and one S(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Er(1), and one S(1) atom. In the fourth O site, O(4) is bonded in a water-like geometry to one Er(1) and one S(1) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Er(1) and one S(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Na(1), one Er(1), and one S(2) atom.
NaEr(SO4)2 crystallizes in the monoclinic P2_1/m space group. Na(1) is bonded in a 7-coordinate geometry to one O(2), two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms. The Na(1)-O(2) bond length is 2.82 Å. There is one shorter (2.46 Å) and one longer (2.63 Å) Na(1)-O(1) bond length. Both Na(1)-O(3) bond lengths are 2.81 Å. Both Na(1)-O(6) bond lengths are 2.30 Å. Er(1) is bonded in a 8-coordinate geometry to one O(2), one O(4), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. The Er(1)-O(2) bond length is 2.25 Å. The Er(1)-O(4) bond length is 2.33 Å. Both Er(1)-O(3) bond lengths are 2.30 Å. There is one shorter (2.37 Å) and one longer (2.79 Å) Er(1)-O(5) bond length. Both Er(1)-O(6) bond lengths are 2.35 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded in a tetrahedral geometry to one O(4), one O(5), and two equivalent O(3) atoms. The S(1)-O(4) bond length is 1.49 Å. The S(1)-O(5) bond length is 1.51 Å. Both S(1)-O(3) bond lengths are 1.48 Å. In the second S site, S(2) is bonded in a tetrahedral geometry to one O(1), one O(2), and two equivalent O(6) atoms. The S(2)-O(1) bond length is 1.46 Å. The S(2)-O(2) bond length is 1.49 Å. Both S(2)-O(6) bond lengths are 1.50 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one S(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Er(1), and one S(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Er(1), and one S(1) atom. In the fourth O site, O(4) is bonded in a water-like geometry to one Er(1) and one S(1) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to two equivalent Er(1) and one S(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Na(1), one Er(1), and one S(2) atom.