The material structure described by Be2Er2SiO7 crystallizes in the tetragonal P-42_1m space group. Be(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form BeO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. Er(1) is bonded in a 8-coordinate geometry to one O(1), three equivalent O(2), and four equivalent O(3) atoms. Si(1) is bonded to four equivalent O(3) atoms to form SiO4 tetrahedra that share corners with four equivalent Be(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Be(1) and two equivalent Er(1) atoms to form a mixture of distorted edge and corner-sharing OEr2Be2 tetrahedra. In the second O site, O(2) is bonded to one Be(1) and three equivalent Er(1) atoms to form distorted OEr3Be tetrahedra that share corners with two equivalent O(1)Er2Be2 tetrahedra, corners with four equivalent O(2)Er3Be tetrahedra,  an edgeedge with one O(1)Er2Be2 tetrahedra, and  an edgeedge with one O(2)Er3Be tetrahedra. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Be(1), two equivalent Er(1), and one Si(1) atom. is represented by the CIF card [CIF]
data_Er2Be2SiO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.282
_cell_length_b   7.282
_cell_length_c   4.759
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   252.389
_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  0.159  0.341  0.509  1.0
  Er  Er1  1  0.841  0.659  0.509  1.0
  Er  Er2  1  0.659  0.159  0.491  1.0
  Er  Er3  1  0.341  0.841  0.491  1.0
  Be  Be4  1  0.636  0.864  0.955  1.0
  Be  Be5  1  0.364  0.136  0.955  1.0
  Be  Be6  1  0.136  0.636  0.045  1.0
  Be  Be7  1  0.864  0.364  0.045  1.0
  Si  Si8  1  0.000  0.000  0.000  1.0
  Si  Si9  1  0.500  0.500  0.000  1.0
  O  O10  1  0.000  0.500  0.190  1.0
  O  O11  1  0.500  0.000  0.810  1.0
  O  O12  1  0.641  0.859  0.288  1.0
  O  O13  1  0.359  0.141  0.288  1.0
  O  O14  1  0.141  0.641  0.712  1.0
  O  O15  1  0.859  0.359  0.712  1.0
  O  O16  1  0.080  0.837  0.204  1.0
  O  O17  1  0.920  0.163  0.204  1.0
  O  O18  1  0.163  0.080  0.796  1.0
  O  O19  1  0.420  0.337  0.796  1.0
  O  O20  1  0.837  0.920  0.796  1.0
  O  O21  1  0.580  0.663  0.796  1.0
  O  O22  1  0.337  0.580  0.204  1.0
  O  O23  1  0.663  0.420  0.204  1.0
[/CIF]
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The material structure described by Be2Er2SiO7 crystallizes in the tetragonal P-42_1m space group. Be(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form BeO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. Er(1) is bonded in a 8-coordinate geometry to one O(1), three equivalent O(2), and four equivalent O(3) atoms. Si(1) is bonded to four equivalent O(3) atoms to form SiO4 tetrahedra that share corners with four equivalent Be(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Be(1) and two equivalent Er(1) atoms to form a mixture of distorted edge and corner-sharing OEr2Be2 tetrahedra. In the second O site, O(2) is bonded to one Be(1) and three equivalent Er(1) atoms to form distorted OEr3Be tetrahedra that share corners with two equivalent O(1)Er2Be2 tetrahedra, corners with four equivalent O(2)Er3Be tetrahedra,  an edgeedge with one O(1)Er2Be2 tetrahedra, and  an edgeedge with one O(2)Er3Be tetrahedra. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Be(1), two equivalent Er(1), and one Si(1) atom. is represented by the CIF card [CIF]
data_Er2Be2SiO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.282
_cell_length_b   7.282
_cell_length_c   4.759
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   252.389
_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  0.159  0.341  0.509  1.0
  Er  Er1  1  0.841  0.659  0.509  1.0
  Er  Er2  1  0.659  0.159  0.491  1.0
  Er  Er3  1  0.341  0.841  0.491  1.0
  Be  Be4  1  0.636  0.864  0.955  1.0
  Be  Be5  1  0.364  0.136  0.955  1.0
  Be  Be6  1  0.136  0.636  0.045  1.0
  Be  Be7  1  0.864  0.364  0.045  1.0
  Si  Si8  1  0.000  0.000  0.000  1.0
  Si  Si9  1  0.500  0.500  0.000  1.0
  O  O10  1  0.000  0.500  0.190  1.0
  O  O11  1  0.500  0.000  0.810  1.0
  O  O12  1  0.641  0.859  0.288  1.0
  O  O13  1  0.359  0.141  0.288  1.0
  O  O14  1  0.141  0.641  0.712  1.0
  O  O15  1  0.859  0.359  0.712  1.0
  O  O16  1  0.080  0.837  0.204  1.0
  O  O17  1  0.920  0.163  0.204  1.0
  O  O18  1  0.163  0.080  0.796  1.0
  O  O19  1  0.420  0.337  0.796  1.0
  O  O20  1  0.837  0.920  0.796  1.0
  O  O21  1  0.580  0.663  0.796  1.0
  O  O22  1  0.337  0.580  0.204  1.0
  O  O23  1  0.663  0.420  0.204  1.0
[/CIF]
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