The structure described by BaCuSi2O6 crystallizes in the tetragonal I4_1/a space group. Ba(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(6) atoms. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Si(1), and one Si(2) atom. In the second O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(2), and one Si(1) atom. In the third O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(1), and one Si(2) atom. In the fourth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(1), and one Si(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Si(1), and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(2), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_BaCu(SiO3)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.180
_cell_length_b   7.180
_cell_length_c   7.540
_cell_angle_alpha   118.431
_cell_angle_beta   118.431
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   287.366
_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
  Ba  Ba0  1  0.250  0.750  1.000  1.0
  Ba  Ba1  1  0.750  0.250  0.000  1.0
  Cu  Cu2  1  0.622  0.622  0.744  1.0
  Cu  Cu3  1  0.378  0.378  0.256  1.0
  O  O4  1  1.000  0.265  0.500  1.0
  O  O5  1  0.000  0.735  0.500  1.0
  O  O6  1  0.265  0.000  0.500  1.0
  O  O7  1  0.735  1.000  0.500  1.0
  O  O8  1  0.182  0.182  0.249  1.0
  O  O9  1  0.567  0.567  0.249  1.0
  O  O10  1  0.182  0.567  0.249  1.0
  O  O11  1  0.567  0.182  0.249  1.0
  O  O12  1  0.818  0.818  0.751  1.0
  O  O13  1  0.433  0.433  0.751  1.0
  O  O14  1  0.818  0.433  0.751  1.0
  O  O15  1  0.433  0.818  0.751  1.0
  Si  Si16  1  0.774  0.226  0.500  1.0
  Si  Si17  1  0.226  0.774  0.500  1.0
  Si  Si18  1  0.226  0.226  0.500  1.0
  Si  Si19  1  0.774  0.774  0.500  1.0
[/CIF]
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The structure described by BaCuSi2O6 crystallizes in the tetragonal I4_1/a space group. Ba(1) is bonded in a 12-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(6) atoms. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Si(1), and one Si(2) atom. In the second O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(2), and one Si(1) atom. In the third O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(1), and one Si(2) atom. In the fourth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(1), and one Si(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1), one Si(1), and one Si(2) atom. In the sixth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Cu(2), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_BaCu(SiO3)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.180
_cell_length_b   7.180
_cell_length_c   7.540
_cell_angle_alpha   118.431
_cell_angle_beta   118.431
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   287.366
_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
  Ba  Ba0  1  0.250  0.750  1.000  1.0
  Ba  Ba1  1  0.750  0.250  0.000  1.0
  Cu  Cu2  1  0.622  0.622  0.744  1.0
  Cu  Cu3  1  0.378  0.378  0.256  1.0
  O  O4  1  1.000  0.265  0.500  1.0
  O  O5  1  0.000  0.735  0.500  1.0
  O  O6  1  0.265  0.000  0.500  1.0
  O  O7  1  0.735  1.000  0.500  1.0
  O  O8  1  0.182  0.182  0.249  1.0
  O  O9  1  0.567  0.567  0.249  1.0
  O  O10  1  0.182  0.567  0.249  1.0
  O  O11  1  0.567  0.182  0.249  1.0
  O  O12  1  0.818  0.818  0.751  1.0
  O  O13  1  0.433  0.433  0.751  1.0
  O  O14  1  0.818  0.433  0.751  1.0
  O  O15  1  0.433  0.818  0.751  1.0
  Si  Si16  1  0.774  0.226  0.500  1.0
  Si  Si17  1  0.226  0.774  0.500  1.0
  Si  Si18  1  0.226  0.226  0.500  1.0
  Si  Si19  1  0.774  0.774  0.500  1.0
[/CIF]
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