The structure described by Be2Nd2SiO7 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. Nd(1) is bonded in a 8-coordinate geometry to one O(2), three equivalent O(1), 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 one Be(1) and three equivalent Nd(1) atoms to form a mixture of distorted edge and corner-sharing ONd3Be tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Be(1) and two equivalent Nd(1) atoms. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Be(1), two equivalent Nd(1), and one Si(1) atom. is represented by the CIF file [CIF]
data_Nd2Be2SiO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.518
_cell_length_b   7.518
_cell_length_c   4.906
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   277.325
_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
  Nd  Nd0  1  0.839  0.661  0.494  1.0
  Nd  Nd1  1  0.339  0.839  0.506  1.0
  Nd  Nd2  1  0.661  0.161  0.506  1.0
  Nd  Nd3  1  0.161  0.339  0.494  1.0
  Be  Be4  1  0.135  0.635  0.964  1.0
  Be  Be5  1  0.635  0.865  0.036  1.0
  Be  Be6  1  0.865  0.365  0.964  1.0
  Be  Be7  1  0.365  0.135  0.036  1.0
  Si  Si8  1  0.500  0.500  0.000  1.0
  Si  Si9  1  0.000  0.000  0.000  1.0
  O  O10  1  0.859  0.359  0.288  1.0
  O  O11  1  0.359  0.141  0.712  1.0
  O  O12  1  0.141  0.641  0.288  1.0
  O  O13  1  0.641  0.859  0.712  1.0
  O  O14  1  0.500  0.000  0.171  1.0
  O  O15  1  0.000  0.500  0.829  1.0
  O  O16  1  0.077  0.836  0.810  1.0
  O  O17  1  0.164  0.077  0.190  1.0
  O  O18  1  0.836  0.923  0.190  1.0
  O  O19  1  0.923  0.164  0.810  1.0
  O  O20  1  0.577  0.664  0.190  1.0
  O  O21  1  0.423  0.336  0.190  1.0
  O  O22  1  0.336  0.577  0.810  1.0
  O  O23  1  0.664  0.423  0.810  1.0
[/CIF]
.
The structure described by Be2Nd2SiO7 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. Nd(1) is bonded in a 8-coordinate geometry to one O(2), three equivalent O(1), 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 one Be(1) and three equivalent Nd(1) atoms to form a mixture of distorted edge and corner-sharing ONd3Be tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Be(1) and two equivalent Nd(1) atoms. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Be(1), two equivalent Nd(1), and one Si(1) atom. is represented by the CIF file [CIF]
data_Nd2Be2SiO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.518
_cell_length_b   7.518
_cell_length_c   4.906
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   277.325
_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
  Nd  Nd0  1  0.839  0.661  0.494  1.0
  Nd  Nd1  1  0.339  0.839  0.506  1.0
  Nd  Nd2  1  0.661  0.161  0.506  1.0
  Nd  Nd3  1  0.161  0.339  0.494  1.0
  Be  Be4  1  0.135  0.635  0.964  1.0
  Be  Be5  1  0.635  0.865  0.036  1.0
  Be  Be6  1  0.865  0.365  0.964  1.0
  Be  Be7  1  0.365  0.135  0.036  1.0
  Si  Si8  1  0.500  0.500  0.000  1.0
  Si  Si9  1  0.000  0.000  0.000  1.0
  O  O10  1  0.859  0.359  0.288  1.0
  O  O11  1  0.359  0.141  0.712  1.0
  O  O12  1  0.141  0.641  0.288  1.0
  O  O13  1  0.641  0.859  0.712  1.0
  O  O14  1  0.500  0.000  0.171  1.0
  O  O15  1  0.000  0.500  0.829  1.0
  O  O16  1  0.077  0.836  0.810  1.0
  O  O17  1  0.164  0.077  0.190  1.0
  O  O18  1  0.836  0.923  0.190  1.0
  O  O19  1  0.923  0.164  0.810  1.0
  O  O20  1  0.577  0.664  0.190  1.0
  O  O21  1  0.423  0.336  0.190  1.0
  O  O22  1  0.336  0.577  0.810  1.0
  O  O23  1  0.664  0.423  0.810  1.0
[/CIF]
.