Er2CO7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 8-coordinate geometry to one O(3), one O(4), one O(5), one O(6), two equivalent O(1), and two equivalent O(2) atoms. In the second Er site, Er(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(4), one O(7), two equivalent O(5), and two equivalent O(6) atoms. C(1) is bonded in a trigonal planar geometry to one O(3), one O(4), and one O(7) atom. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a trigonal planar geometry to one Er(1) and two equivalent Er(2) atoms. In the second O site, O(7) is bonded in a distorted water-like geometry to one Er(2) and one C(1) atom. In the third O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Er(2) and two equivalent Er(1) atoms. In the fourth O site, O(2) is bonded in a trigonal non-coplanar geometry to one Er(2) and two equivalent Er(1) atoms. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to one Er(1) and one C(1) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Er(1), one Er(2), and one C(1) atom. In the seventh O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Er(1) and two equivalent Er(2) atoms.
Er2CO7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 8-coordinate geometry to one O(3), one O(4), one O(5), one O(6), two equivalent O(1), and two equivalent O(2) atoms. The Er(1)-O(3) bond length is 2.25 Å. The Er(1)-O(4) bond length is 2.27 Å. The Er(1)-O(5) bond length is 2.77 Å. The Er(1)-O(6) bond length is 2.28 Å. There is one shorter (2.33 Å) and one longer (2.34 Å) Er(1)-O(1) bond length. There is one shorter (2.24 Å) and one longer (2.35 Å) Er(1)-O(2) bond length. In the second Er site, Er(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(4), one O(7), two equivalent O(5), and two equivalent O(6) atoms. The Er(2)-O(1) bond length is 2.49 Å. The Er(2)-O(2) bond length is 2.29 Å. The Er(2)-O(4) bond length is 2.52 Å. The Er(2)-O(7) bond length is 2.34 Å. There is one shorter (2.24 Å) and one longer (2.25 Å) Er(2)-O(5) bond length. Both Er(2)-O(6) bond lengths are 2.28 Å. C(1) is bonded in a trigonal planar geometry to one O(3), one O(4), and one O(7) atom. The C(1)-O(3) bond length is 1.27 Å. The C(1)-O(4) bond length is 1.31 Å. The C(1)-O(7) bond length is 1.28 Å. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a trigonal planar geometry to one Er(1) and two equivalent Er(2) atoms. In the second O site, O(7) is bonded in a distorted water-like geometry to one Er(2) and one C(1) atom. In the third O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Er(2) and two equivalent Er(1) atoms. In the fourth O site, O(2) is bonded in a trigonal non-coplanar geometry to one Er(2) and two equivalent Er(1) atoms. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to one Er(1) and one C(1) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Er(1), one Er(2), and one C(1) atom. In the seventh O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Er(1) and two equivalent Er(2) atoms.