The compound described by LiBe4Er4(SiO7)2 crystallizes in the monoclinic Cm space group. Li(1) is bonded in a 3-coordinate geometry to two equivalent Er(2), one O(1), two equivalent O(6), and two equivalent O(9) atoms. There are three inequivalent Be sites. In the first Be site, Be(1) is bonded to one O(2), one O(3), and two equivalent O(9) atoms to form distorted BeO4 tetrahedra that share  a cornercorner with one Be(2)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. In the second Be site, Be(2) is bonded to one O(2), one O(4), and two equivalent O(8) atoms to form BeO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. In the third Be site, Be(3) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form distorted BeO4 tetrahedra that share  a cornercorner with one Be(3)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded in a 8-coordinate geometry to one O(1), one O(4), two equivalent O(5), two equivalent O(7), and two equivalent O(8) atoms. In the second Er site, Er(2) is bonded in a 10-coordinate geometry to two equivalent Li(1), one O(1), one O(3), two equivalent O(5), two equivalent O(6), and two equivalent O(9) atoms. In the third Er site, Er(3) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. Si(1) is bonded to one O(6), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra,  a cornercorner with one Be(2)O4 tetrahedra, and corners with two equivalent Be(3)O4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(9) is bonded in a 5-coordinate geometry to one Li(1), one Be(1), one Er(2), one Er(3), and one Si(1) atom. In the second O site, O(1) is bonded in a 5-coordinate geometry to one Li(1), two equivalent Be(3), one Er(1), and one Er(2) atom. In the third O site, O(2) is bonded to one Be(1), one Be(2), and two equivalent Er(3) atoms to form a mixture of distorted corner and edge-sharing OEr2Be2 tetrahedra. In the fourth O site, O(3) is bonded in a 1-coordinate geometry to one Be(1), one Er(2), and two equivalent Er(3) atoms. In the fifth O site, O(4) is bonded to one Be(2), one Er(1), and two equivalent Er(3) atoms to form a mixture of distorted corner and edge-sharing OEr3Be tetrahedra. In the sixth O site, O(5) is bonded in a 4-coordinate geometry to one Be(3), one Er(1), one Er(2), and one Er(3) atom. In the seventh O site, O(6) is bonded in a 5-coordinate geometry to one Li(1), one Be(3), one Er(2), one Er(3), and one Si(1) atom. In the eighth O site, O(7) is bonded in a 4-coordinate geometry to one Be(3), one Er(1), one Er(3), and one Si(1) atom. In the ninth O site, O(8) is bonded in a 4-coordinate geometry to one Be(2), one Er(1), one Er(3), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_LiEr4Be4(SiO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.866
_cell_length_b   7.342
_cell_length_c   7.342
_cell_angle_alpha   89.169
_cell_angle_beta   90.157
_cell_angle_gamma   90.157
_symmetry_Int_Tables_number   1
_cell_volume   262.290
_cell_formula_units_Z   1
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
  Li  Li0  1  0.004  0.838  0.338  1.0
  Er  Er1  1  0.510  0.157  0.657  1.0
  Er  Er2  1  0.507  0.842  0.342  1.0
  Er  Er3  1  0.485  0.654  0.839  1.0
  Er  Er4  1  0.485  0.339  0.154  1.0
  Be  Be5  1  0.966  0.625  0.125  1.0
  Be  Be6  1  0.958  0.359  0.859  1.0
  Be  Be7  1  0.035  0.150  0.369  1.0
  Be  Be8  1  0.035  0.869  0.650  1.0
  Si  Si9  1  0.002  0.001  1.000  1.0
  Si  Si10  1  0.002  0.500  0.501  1.0
  O  O11  1  0.173  0.005  0.505  1.0
  O  O12  1  0.810  0.495  0.995  1.0
  O  O13  1  0.295  0.627  0.127  1.0
  O  O14  1  0.288  0.354  0.854  1.0
  O  O15  1  0.707  0.150  0.361  1.0
  O  O16  1  0.707  0.861  0.650  1.0
  O  O17  1  0.191  0.086  0.166  1.0
  O  O18  1  0.204  0.918  0.842  1.0
  O  O19  1  0.800  0.159  0.914  1.0
  O  O20  1  0.800  0.414  0.659  1.0
  O  O21  1  0.814  0.835  0.087  1.0
  O  O22  1  0.814  0.588  0.335  1.0
  O  O23  1  0.204  0.342  0.418  1.0
  O  O24  1  0.191  0.666  0.586  1.0
[/CIF]
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The compound described by LiBe4Er4(SiO7)2 crystallizes in the monoclinic Cm space group. Li(1) is bonded in a 3-coordinate geometry to two equivalent Er(2), one O(1), two equivalent O(6), and two equivalent O(9) atoms. There are three inequivalent Be sites. In the first Be site, Be(1) is bonded to one O(2), one O(3), and two equivalent O(9) atoms to form distorted BeO4 tetrahedra that share  a cornercorner with one Be(2)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. In the second Be site, Be(2) is bonded to one O(2), one O(4), and two equivalent O(8) atoms to form BeO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. In the third Be site, Be(3) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form distorted BeO4 tetrahedra that share  a cornercorner with one Be(3)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded in a 8-coordinate geometry to one O(1), one O(4), two equivalent O(5), two equivalent O(7), and two equivalent O(8) atoms. In the second Er site, Er(2) is bonded in a 10-coordinate geometry to two equivalent Li(1), one O(1), one O(3), two equivalent O(5), two equivalent O(6), and two equivalent O(9) atoms. In the third Er site, Er(3) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. Si(1) is bonded to one O(6), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra,  a cornercorner with one Be(2)O4 tetrahedra, and corners with two equivalent Be(3)O4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(9) is bonded in a 5-coordinate geometry to one Li(1), one Be(1), one Er(2), one Er(3), and one Si(1) atom. In the second O site, O(1) is bonded in a 5-coordinate geometry to one Li(1), two equivalent Be(3), one Er(1), and one Er(2) atom. In the third O site, O(2) is bonded to one Be(1), one Be(2), and two equivalent Er(3) atoms to form a mixture of distorted corner and edge-sharing OEr2Be2 tetrahedra. In the fourth O site, O(3) is bonded in a 1-coordinate geometry to one Be(1), one Er(2), and two equivalent Er(3) atoms. In the fifth O site, O(4) is bonded to one Be(2), one Er(1), and two equivalent Er(3) atoms to form a mixture of distorted corner and edge-sharing OEr3Be tetrahedra. In the sixth O site, O(5) is bonded in a 4-coordinate geometry to one Be(3), one Er(1), one Er(2), and one Er(3) atom. In the seventh O site, O(6) is bonded in a 5-coordinate geometry to one Li(1), one Be(3), one Er(2), one Er(3), and one Si(1) atom. In the eighth O site, O(7) is bonded in a 4-coordinate geometry to one Be(3), one Er(1), one Er(3), and one Si(1) atom. In the ninth O site, O(8) is bonded in a 4-coordinate geometry to one Be(2), one Er(1), one Er(3), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_LiEr4Be4(SiO7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.866
_cell_length_b   7.342
_cell_length_c   7.342
_cell_angle_alpha   89.169
_cell_angle_beta   90.157
_cell_angle_gamma   90.157
_symmetry_Int_Tables_number   1
_cell_volume   262.290
_cell_formula_units_Z   1
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
  Li  Li0  1  0.004  0.838  0.338  1.0
  Er  Er1  1  0.510  0.157  0.657  1.0
  Er  Er2  1  0.507  0.842  0.342  1.0
  Er  Er3  1  0.485  0.654  0.839  1.0
  Er  Er4  1  0.485  0.339  0.154  1.0
  Be  Be5  1  0.966  0.625  0.125  1.0
  Be  Be6  1  0.958  0.359  0.859  1.0
  Be  Be7  1  0.035  0.150  0.369  1.0
  Be  Be8  1  0.035  0.869  0.650  1.0
  Si  Si9  1  0.002  0.001  1.000  1.0
  Si  Si10  1  0.002  0.500  0.501  1.0
  O  O11  1  0.173  0.005  0.505  1.0
  O  O12  1  0.810  0.495  0.995  1.0
  O  O13  1  0.295  0.627  0.127  1.0
  O  O14  1  0.288  0.354  0.854  1.0
  O  O15  1  0.707  0.150  0.361  1.0
  O  O16  1  0.707  0.861  0.650  1.0
  O  O17  1  0.191  0.086  0.166  1.0
  O  O18  1  0.204  0.918  0.842  1.0
  O  O19  1  0.800  0.159  0.914  1.0
  O  O20  1  0.800  0.414  0.659  1.0
  O  O21  1  0.814  0.835  0.087  1.0
  O  O22  1  0.814  0.588  0.335  1.0
  O  O23  1  0.204  0.342  0.418  1.0
  O  O24  1  0.191  0.666  0.586  1.0
[/CIF]
.