The crystal structure described by Er2Cu(B2O5)2 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c space group. Er(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. Cu(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted CuO6 octahedra that share corners with two equivalent B(2)O4 tetrahedra, corners with four equivalent B(1)O4 tetrahedra, and edges with two equivalent B(2)O4 tetrahedra. There are two inequivalent B sites. In the first B site, B(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form BO4 tetrahedra that share corners with two equivalent Cu(1)O6 octahedra and corners with three equivalent B(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 67-70°. In the second B site, B(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form BO4 tetrahedra that share  a cornercorner with one Cu(1)O6 octahedra, corners with three equivalent B(1)O4 tetrahedra, and  an edgeedge with one Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Er(1), one Cu(1), one B(1), and one B(2) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Er(1), one B(1), and one B(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Er(1), one Cu(1), one B(1), and one B(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Er(1), one Cu(1), and one B(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Er(1) and one B(1) atom. is represented by the CIF card [CIF]
data_Er2Cu(B2O5)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.269
_cell_length_b   4.593
_cell_length_c   9.345
_cell_angle_alpha   89.612
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   311.993
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Er  Er0  1  0.396  0.004  0.835  1.0
  Er  Er1  1  0.896  0.996  0.665  1.0
  Er  Er2  1  0.104  0.004  0.335  1.0
  Er  Er3  1  0.604  0.996  0.165  1.0
  Cu  Cu4  1  0.000  0.000  0.000  1.0
  Cu  Cu5  1  0.500  0.000  0.500  1.0
  B  B6  1  0.268  0.539  0.080  1.0
  B  B7  1  0.768  0.461  0.420  1.0
  B  B8  1  0.732  0.461  0.920  1.0
  B  B9  1  0.232  0.539  0.580  1.0
  B  B10  1  0.598  0.528  0.662  1.0
  B  B11  1  0.098  0.472  0.838  1.0
  B  B12  1  0.902  0.528  0.162  1.0
  B  B13  1  0.402  0.472  0.338  1.0
  O  O14  1  0.223  0.359  0.952  1.0
  O  O15  1  0.723  0.641  0.548  1.0
  O  O16  1  0.835  0.658  0.301  1.0
  O  O17  1  0.335  0.342  0.199  1.0
  O  O18  1  0.165  0.342  0.699  1.0
  O  O19  1  0.665  0.658  0.801  1.0
  O  O20  1  0.088  0.677  0.138  1.0
  O  O21  1  0.588  0.323  0.362  1.0
  O  O22  1  0.912  0.323  0.862  1.0
  O  O23  1  0.412  0.677  0.638  1.0
  O  O24  1  0.911  0.214  0.166  1.0
  O  O25  1  0.411  0.786  0.334  1.0
  O  O26  1  0.089  0.786  0.834  1.0
  O  O27  1  0.589  0.214  0.666  1.0
  O  O28  1  0.111  0.771  0.542  1.0
  O  O29  1  0.611  0.229  0.958  1.0
  O  O30  1  0.889  0.229  0.458  1.0
  O  O31  1  0.389  0.771  0.042  1.0
  O  O32  1  0.777  0.641  0.048  1.0
  O  O33  1  0.277  0.359  0.452  1.0
[/CIF]
.
The crystal structure described by Er2Cu(B2O5)2 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c space group. Er(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. Cu(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted CuO6 octahedra that share corners with two equivalent B(2)O4 tetrahedra, corners with four equivalent B(1)O4 tetrahedra, and edges with two equivalent B(2)O4 tetrahedra. There are two inequivalent B sites. In the first B site, B(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form BO4 tetrahedra that share corners with two equivalent Cu(1)O6 octahedra and corners with three equivalent B(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 67-70°. In the second B site, B(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form BO4 tetrahedra that share  a cornercorner with one Cu(1)O6 octahedra, corners with three equivalent B(1)O4 tetrahedra, and  an edgeedge with one Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Er(1), one Cu(1), one B(1), and one B(2) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Er(1), one B(1), and one B(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Er(1), one Cu(1), one B(1), and one B(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Er(1), one Cu(1), and one B(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Er(1) and one B(1) atom. is represented by the CIF card [CIF]
data_Er2Cu(B2O5)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.269
_cell_length_b   4.593
_cell_length_c   9.345
_cell_angle_alpha   89.612
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   311.993
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Er  Er0  1  0.396  0.004  0.835  1.0
  Er  Er1  1  0.896  0.996  0.665  1.0
  Er  Er2  1  0.104  0.004  0.335  1.0
  Er  Er3  1  0.604  0.996  0.165  1.0
  Cu  Cu4  1  0.000  0.000  0.000  1.0
  Cu  Cu5  1  0.500  0.000  0.500  1.0
  B  B6  1  0.268  0.539  0.080  1.0
  B  B7  1  0.768  0.461  0.420  1.0
  B  B8  1  0.732  0.461  0.920  1.0
  B  B9  1  0.232  0.539  0.580  1.0
  B  B10  1  0.598  0.528  0.662  1.0
  B  B11  1  0.098  0.472  0.838  1.0
  B  B12  1  0.902  0.528  0.162  1.0
  B  B13  1  0.402  0.472  0.338  1.0
  O  O14  1  0.223  0.359  0.952  1.0
  O  O15  1  0.723  0.641  0.548  1.0
  O  O16  1  0.835  0.658  0.301  1.0
  O  O17  1  0.335  0.342  0.199  1.0
  O  O18  1  0.165  0.342  0.699  1.0
  O  O19  1  0.665  0.658  0.801  1.0
  O  O20  1  0.088  0.677  0.138  1.0
  O  O21  1  0.588  0.323  0.362  1.0
  O  O22  1  0.912  0.323  0.862  1.0
  O  O23  1  0.412  0.677  0.638  1.0
  O  O24  1  0.911  0.214  0.166  1.0
  O  O25  1  0.411  0.786  0.334  1.0
  O  O26  1  0.089  0.786  0.834  1.0
  O  O27  1  0.589  0.214  0.666  1.0
  O  O28  1  0.111  0.771  0.542  1.0
  O  O29  1  0.611  0.229  0.958  1.0
  O  O30  1  0.889  0.229  0.458  1.0
  O  O31  1  0.389  0.771  0.042  1.0
  O  O32  1  0.777  0.641  0.048  1.0
  O  O33  1  0.277  0.359  0.452  1.0
[/CIF]
.