The compound described by Be4Si2O9 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Be sites. In the first Be site, Be(1) is bonded to one O(1), one O(6), and two equivalent O(2) atoms to form BeO4 tetrahedra that share  a cornercorner with one Be(2)O4 tetrahedra, corners with three equivalent Be(1)O4 tetrahedra, and corners with three equivalent Si(1)O4 tetrahedra. In the second Be site, Be(2) is bonded to one O(1), one O(5), and two equivalent O(3) atoms to form BeO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra, corners with three equivalent Be(2)O4 tetrahedra, and corners with three equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra, corners with three equivalent Be(1)O4 tetrahedra, and corners with three equivalent Be(2)O4 tetrahedra. There are six inequivalent O sites. In the first O site, O(3) is bonded in a trigonal planar geometry to two equivalent Be(2) and one Si(1) atom. In the second O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the third O site, O(5) is bonded in a bent 150 degrees geometry to two equivalent Be(2) atoms. In the fourth O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Be(1) atoms. In the fifth O site, O(1) is bonded in a trigonal planar geometry to one Be(1), one Be(2), and one Si(1) atom. In the sixth O site, O(2) is bonded in a trigonal planar geometry to two equivalent Be(1) and one Si(1) atom. is represented by the CIF card [CIF]
data_Be4Si2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.655
_cell_length_b   8.696
_cell_length_c   9.076
_cell_angle_alpha   118.626
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   322.458
_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
  Be  Be0  1  0.623  0.130  0.905  1.0
  Be  Be1  1  0.623  0.775  0.905  1.0
  Be  Be2  1  0.123  0.870  0.095  1.0
  Be  Be3  1  0.123  0.225  0.095  1.0
  Be  Be4  1  0.622  0.102  0.568  1.0
  Be  Be5  1  0.622  0.466  0.568  1.0
  Be  Be6  1  0.122  0.898  0.432  1.0
  Be  Be7  1  0.122  0.534  0.432  1.0
  Si  Si8  1  0.125  0.201  0.765  1.0
  Si  Si9  1  0.125  0.563  0.765  1.0
  Si  Si10  1  0.625  0.799  0.235  1.0
  Si  Si11  1  0.625  0.437  0.235  1.0
  O  O12  1  0.467  0.146  0.749  1.0
  O  O13  1  0.467  0.603  0.749  1.0
  O  O14  1  0.967  0.854  0.251  1.0
  O  O15  1  0.967  0.397  0.251  1.0
  O  O16  1  0.966  0.181  0.916  1.0
  O  O17  1  0.966  0.735  0.916  1.0
  O  O18  1  0.466  0.819  0.084  1.0
  O  O19  1  0.466  0.265  0.084  1.0
  O  O20  1  0.967  0.069  0.586  1.0
  O  O21  1  0.967  0.516  0.586  1.0
  O  O22  1  0.467  0.931  0.414  1.0
  O  O23  1  0.467  0.484  0.414  1.0
  O  O24  1  0.086  0.405  0.811  1.0
  O  O25  1  0.586  0.595  0.189  1.0
  O  O26  1  0.552  0.275  0.551  1.0
  O  O27  1  0.052  0.725  0.449  1.0
  O  O28  1  0.553  0.942  0.885  1.0
  O  O29  1  0.053  0.058  0.115  1.0
[/CIF]
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The compound described by Be4Si2O9 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Be sites. In the first Be site, Be(1) is bonded to one O(1), one O(6), and two equivalent O(2) atoms to form BeO4 tetrahedra that share  a cornercorner with one Be(2)O4 tetrahedra, corners with three equivalent Be(1)O4 tetrahedra, and corners with three equivalent Si(1)O4 tetrahedra. In the second Be site, Be(2) is bonded to one O(1), one O(5), and two equivalent O(3) atoms to form BeO4 tetrahedra that share  a cornercorner with one Be(1)O4 tetrahedra, corners with three equivalent Be(2)O4 tetrahedra, and corners with three equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra, corners with three equivalent Be(1)O4 tetrahedra, and corners with three equivalent Be(2)O4 tetrahedra. There are six inequivalent O sites. In the first O site, O(3) is bonded in a trigonal planar geometry to two equivalent Be(2) and one Si(1) atom. In the second O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the third O site, O(5) is bonded in a bent 150 degrees geometry to two equivalent Be(2) atoms. In the fourth O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Be(1) atoms. In the fifth O site, O(1) is bonded in a trigonal planar geometry to one Be(1), one Be(2), and one Si(1) atom. In the sixth O site, O(2) is bonded in a trigonal planar geometry to two equivalent Be(1) and one Si(1) atom. is represented by the CIF card [CIF]
data_Be4Si2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.655
_cell_length_b   8.696
_cell_length_c   9.076
_cell_angle_alpha   118.626
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   322.458
_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
  Be  Be0  1  0.623  0.130  0.905  1.0
  Be  Be1  1  0.623  0.775  0.905  1.0
  Be  Be2  1  0.123  0.870  0.095  1.0
  Be  Be3  1  0.123  0.225  0.095  1.0
  Be  Be4  1  0.622  0.102  0.568  1.0
  Be  Be5  1  0.622  0.466  0.568  1.0
  Be  Be6  1  0.122  0.898  0.432  1.0
  Be  Be7  1  0.122  0.534  0.432  1.0
  Si  Si8  1  0.125  0.201  0.765  1.0
  Si  Si9  1  0.125  0.563  0.765  1.0
  Si  Si10  1  0.625  0.799  0.235  1.0
  Si  Si11  1  0.625  0.437  0.235  1.0
  O  O12  1  0.467  0.146  0.749  1.0
  O  O13  1  0.467  0.603  0.749  1.0
  O  O14  1  0.967  0.854  0.251  1.0
  O  O15  1  0.967  0.397  0.251  1.0
  O  O16  1  0.966  0.181  0.916  1.0
  O  O17  1  0.966  0.735  0.916  1.0
  O  O18  1  0.466  0.819  0.084  1.0
  O  O19  1  0.466  0.265  0.084  1.0
  O  O20  1  0.967  0.069  0.586  1.0
  O  O21  1  0.967  0.516  0.586  1.0
  O  O22  1  0.467  0.931  0.414  1.0
  O  O23  1  0.467  0.484  0.414  1.0
  O  O24  1  0.086  0.405  0.811  1.0
  O  O25  1  0.586  0.595  0.189  1.0
  O  O26  1  0.552  0.275  0.551  1.0
  O  O27  1  0.052  0.725  0.449  1.0
  O  O28  1  0.553  0.942  0.885  1.0
  O  O29  1  0.053  0.058  0.115  1.0
[/CIF]
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