The crystal structure described by LiBe4Er4(SiO7)2 crystallizes in the tetragonal P-4 space group. Li(1) is bonded in a 4-coordinate geometry to four equivalent O(3) atoms. Be(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form BeO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. Er(1) is bonded in a 8-coordinate geometry to one O(1), two equivalent O(3), two equivalent O(4), and three equivalent O(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to four equivalent O(3) atoms to form SiO4 tetrahedra that share corners with four equivalent Be(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to four equivalent O(4) atoms to form SiO4 tetrahedra that share corners with four equivalent Be(1)O4 tetrahedra. There are four 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 corner and edge-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 3-coordinate geometry to one Li(1), one Be(1), two equivalent Er(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Be(1), two equivalent Er(1), and one Si(2) 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   4.765
_cell_length_b   7.402
_cell_length_c   7.402
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   261.041
_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  0.500  0.000  0.000  1.0
  Er  Er1  1  0.512  0.166  0.643  1.0
  Er  Er2  1  0.512  0.834  0.357  1.0
  Er  Er3  1  0.488  0.643  0.834  1.0
  Er  Er4  1  0.488  0.357  0.166  1.0
  Be  Be5  1  0.962  0.636  0.135  1.0
  Be  Be6  1  0.962  0.364  0.865  1.0
  Be  Be7  1  0.038  0.135  0.364  1.0
  Be  Be8  1  0.038  0.865  0.636  1.0
  Si  Si9  1  0.000  0.000  0.000  1.0
  Si  Si10  1  0.000  0.500  0.500  1.0
  O  O11  1  0.181  0.000  0.500  1.0
  O  O12  1  0.819  0.500  0.000  1.0
  O  O13  1  0.295  0.644  0.140  1.0
  O  O14  1  0.295  0.356  0.860  1.0
  O  O15  1  0.705  0.140  0.356  1.0
  O  O16  1  0.705  0.860  0.644  1.0
  O  O17  1  0.210  0.081  0.158  1.0
  O  O18  1  0.210  0.919  0.842  1.0
  O  O19  1  0.790  0.158  0.919  1.0
  O  O20  1  0.799  0.421  0.663  1.0
  O  O21  1  0.790  0.842  0.081  1.0
  O  O22  1  0.799  0.579  0.337  1.0
  O  O23  1  0.201  0.337  0.421  1.0
  O  O24  1  0.201  0.663  0.579  1.0
[/CIF]
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The crystal structure described by LiBe4Er4(SiO7)2 crystallizes in the tetragonal P-4 space group. Li(1) is bonded in a 4-coordinate geometry to four equivalent O(3) atoms. Be(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form BeO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. Er(1) is bonded in a 8-coordinate geometry to one O(1), two equivalent O(3), two equivalent O(4), and three equivalent O(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to four equivalent O(3) atoms to form SiO4 tetrahedra that share corners with four equivalent Be(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to four equivalent O(4) atoms to form SiO4 tetrahedra that share corners with four equivalent Be(1)O4 tetrahedra. There are four 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 corner and edge-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 3-coordinate geometry to one Li(1), one Be(1), two equivalent Er(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Be(1), two equivalent Er(1), and one Si(2) 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   4.765
_cell_length_b   7.402
_cell_length_c   7.402
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   261.041
_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  0.500  0.000  0.000  1.0
  Er  Er1  1  0.512  0.166  0.643  1.0
  Er  Er2  1  0.512  0.834  0.357  1.0
  Er  Er3  1  0.488  0.643  0.834  1.0
  Er  Er4  1  0.488  0.357  0.166  1.0
  Be  Be5  1  0.962  0.636  0.135  1.0
  Be  Be6  1  0.962  0.364  0.865  1.0
  Be  Be7  1  0.038  0.135  0.364  1.0
  Be  Be8  1  0.038  0.865  0.636  1.0
  Si  Si9  1  0.000  0.000  0.000  1.0
  Si  Si10  1  0.000  0.500  0.500  1.0
  O  O11  1  0.181  0.000  0.500  1.0
  O  O12  1  0.819  0.500  0.000  1.0
  O  O13  1  0.295  0.644  0.140  1.0
  O  O14  1  0.295  0.356  0.860  1.0
  O  O15  1  0.705  0.140  0.356  1.0
  O  O16  1  0.705  0.860  0.644  1.0
  O  O17  1  0.210  0.081  0.158  1.0
  O  O18  1  0.210  0.919  0.842  1.0
  O  O19  1  0.790  0.158  0.919  1.0
  O  O20  1  0.799  0.421  0.663  1.0
  O  O21  1  0.790  0.842  0.081  1.0
  O  O22  1  0.799  0.579  0.337  1.0
  O  O23  1  0.201  0.337  0.421  1.0
  O  O24  1  0.201  0.663  0.579  1.0
[/CIF]
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