Er2Cu(GeO4)2 crystallizes in the monoclinic Cm 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(1), one O(10), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom. In the second Er site, Er(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(2), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. Cu(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(4), one O(8), and two equivalent O(1) atoms. There are three inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a tetrahedral geometry to one O(6), one O(9), and two equivalent O(2) atoms. In the second Ge site, Ge(2) is bonded to one O(1), one O(10), one O(4), one O(5), and one O(8) atom to form corner-sharing GeO5 trigonal bipyramids. In the third Ge site, Ge(3) is bonded to one O(3), one O(7), and two equivalent O(5) atoms to form corner-sharing GeO4 tetrahedra. There are ten inequivalent O sites. In the first O site, O(9) is bonded in a trigonal planar geometry to two equivalent Er(2) and one Ge(1) atom. In the second O site, O(10) is bonded to one Er(1), one Er(2), one Cu(1), and one Ge(2) atom to form a mixture of distorted corner and edge-sharing OEr2CuGe trigonal pyramids. In the third O site, O(1) is bonded in a 5-coordinate geometry to one Er(1), one Er(2), two equivalent Cu(1), and one Ge(2) atom. In the fourth O site, O(2) is bonded in a 4-coordinate geometry to one Er(1), one Er(2), one Cu(1), and one Ge(1) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to two equivalent Er(1) and one Ge(3) atom. In the sixth O site, O(4) is bonded to one Er(1), one Er(2), one Cu(1), and one Ge(2) atom to form a mixture of distorted corner and edge-sharing OEr2CuGe trigonal pyramids. In the seventh O site, O(5) is bonded in a 4-coordinate geometry to one Er(1), one Er(2), one Ge(2), and one Ge(3) atom. In the eighth O site, O(6) is bonded in a trigonal planar geometry to two equivalent Er(1) and one Ge(1) atom. In the ninth O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Er(2) and one Ge(3) atom. In the tenth O site, O(8) is bonded to one Er(1), one Er(2), one Cu(1), and one Ge(2) atom to form a mixture of corner and edge-sharing OEr2CuGe trigonal pyramids.
Er2Cu(GeO4)2 crystallizes in the monoclinic Cm 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(1), one O(10), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom. The Er(1)-O(1) bond length is 2.47 Å. The Er(1)-O(10) bond length is 2.23 Å. The Er(1)-O(2) bond length is 2.82 Å. The Er(1)-O(3) bond length is 2.26 Å. The Er(1)-O(4) bond length is 2.41 Å. The Er(1)-O(5) bond length is 2.63 Å. The Er(1)-O(6) bond length is 2.25 Å. The Er(1)-O(8) bond length is 2.35 Å. In the second Er site, Er(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(2), one O(4), one O(5), one O(7), one O(8), and one O(9) atom. The Er(2)-O(1) bond length is 2.37 Å. The Er(2)-O(10) bond length is 2.30 Å. The Er(2)-O(2) bond length is 2.54 Å. The Er(2)-O(4) bond length is 2.41 Å. The Er(2)-O(5) bond length is 2.72 Å. The Er(2)-O(7) bond length is 2.28 Å. The Er(2)-O(8) bond length is 2.39 Å. The Er(2)-O(9) bond length is 2.25 Å. Cu(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(4), one O(8), and two equivalent O(1) atoms. The Cu(1)-O(10) bond length is 1.91 Å. The Cu(1)-O(2) bond length is 1.95 Å. The Cu(1)-O(4) bond length is 2.01 Å. The Cu(1)-O(8) bond length is 2.07 Å. There is one shorter (2.44 Å) and one longer (2.64 Å) Cu(1)-O(1) bond length. There are three inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a tetrahedral geometry to one O(6), one O(9), and two equivalent O(2) atoms. The Ge(1)-O(6) bond length is 1.79 Å. The Ge(1)-O(9) bond length is 1.79 Å. Both Ge(1)-O(2) bond lengths are 1.79 Å. In the second Ge site, Ge(2) is bonded to one O(1), one O(10), one O(4), one O(5), and one O(8) atom to form corner-sharing GeO5 trigonal bipyramids. The Ge(2)-O(1) bond length is 1.78 Å. The Ge(2)-O(10) bond length is 1.95 Å. The Ge(2)-O(4) bond length is 1.81 Å. The Ge(2)-O(5) bond length is 1.94 Å. The Ge(2)-O(8) bond length is 1.83 Å. In the third Ge site, Ge(3) is bonded to one O(3), one O(7), and two equivalent O(5) atoms to form corner-sharing GeO4 tetrahedra. The Ge(3)-O(3) bond length is 1.78 Å. The Ge(3)-O(7) bond length is 1.77 Å. Both Ge(3)-O(5) bond lengths are 1.80 Å. There are ten inequivalent O sites. In the first O site, O(9) is bonded in a trigonal planar geometry to two equivalent Er(2) and one Ge(1) atom. In the second O site, O(10) is bonded to one Er(1), one Er(2), one Cu(1), and one Ge(2) atom to form a mixture of distorted corner and edge-sharing OEr2CuGe trigonal pyramids. In the third O site, O(1) is bonded in a 5-coordinate geometry to one Er(1), one Er(2), two equivalent Cu(1), and one Ge(2) atom. In the fourth O site, O(2) is bonded in a 4-coordinate geometry to one Er(1), one Er(2), one Cu(1), and one Ge(1) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to two equivalent Er(1) and one Ge(3) atom. In the sixth O site, O(4) is bonded to one Er(1), one Er(2), one Cu(1), and one Ge(2) atom to form a mixture of distorted corner and edge-sharing OEr2CuGe trigonal pyramids. In the seventh O site, O(5) is bonded in a 4-coordinate geometry to one Er(1), one Er(2), one Ge(2), and one Ge(3) atom. In the eighth O site, O(6) is bonded in a trigonal planar geometry to two equivalent Er(1) and one Ge(1) atom. In the ninth O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Er(2) and one Ge(3) atom. In the tenth O site, O(8) is bonded to one Er(1), one Er(2), one Cu(1), and one Ge(2) atom to form a mixture of corner and edge-sharing OEr2CuGe trigonal pyramids.