The material structure described by Ba2CuSi2O7 crystallizes in the tetragonal P-42_1m space group. Ba(1) is bonded in a 8-coordinate geometry to one O(3), three equivalent O(2), and four equivalent O(1) atoms. Cu(1) is bonded to four equivalent O(1) atoms to form distorted CuO4 tetrahedra that share corners with four equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Cu(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Cu(1), and one Si(1) atom. In the second O site, O(2) is bonded to three equivalent Ba(1) and one Si(1) atom to form a mixture of distorted corner and edge-sharing OBa3Si tetrahedra. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1) and two equivalent Si(1) atoms. is represented by the CIF file [CIF]
data_Ba2CuSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.417
_cell_length_b   8.417
_cell_length_c   5.358
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   379.634
_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  0.667  0.167  0.509  1.0
  Ba  Ba1  1  0.833  0.667  0.491  1.0
  Ba  Ba2  1  0.167  0.333  0.491  1.0
  Ba  Ba3  1  0.333  0.833  0.509  1.0
  Cu  Cu4  1  0.500  0.500  0.000  1.0
  Cu  Cu5  1  0.000  0.000  0.000  1.0
  Si  Si6  1  0.866  0.366  0.976  1.0
  Si  Si7  1  0.634  0.866  0.024  1.0
  Si  Si8  1  0.366  0.134  0.024  1.0
  Si  Si9  1  0.134  0.634  0.976  1.0
  O  O10  1  0.698  0.421  0.844  1.0
  O  O11  1  0.302  0.579  0.844  1.0
  O  O12  1  0.421  0.302  0.156  1.0
  O  O13  1  0.579  0.698  0.156  1.0
  O  O14  1  0.921  0.198  0.844  1.0
  O  O15  1  0.802  0.921  0.156  1.0
  O  O16  1  0.198  0.079  0.156  1.0
  O  O17  1  0.079  0.802  0.844  1.0
  O  O18  1  0.866  0.366  0.277  1.0
  O  O19  1  0.634  0.866  0.723  1.0
  O  O20  1  0.000  0.500  0.870  1.0
  O  O21  1  0.500  0.000  0.130  1.0
  O  O22  1  0.134  0.634  0.277  1.0
  O  O23  1  0.366  0.134  0.723  1.0
[/CIF]
.
The material structure described by Ba2CuSi2O7 crystallizes in the tetragonal P-42_1m space group. Ba(1) is bonded in a 8-coordinate geometry to one O(3), three equivalent O(2), and four equivalent O(1) atoms. Cu(1) is bonded to four equivalent O(1) atoms to form distorted CuO4 tetrahedra that share corners with four equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Cu(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Cu(1), and one Si(1) atom. In the second O site, O(2) is bonded to three equivalent Ba(1) and one Si(1) atom to form a mixture of distorted corner and edge-sharing OBa3Si tetrahedra. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Ba(1) and two equivalent Si(1) atoms. is represented by the CIF file [CIF]
data_Ba2CuSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.417
_cell_length_b   8.417
_cell_length_c   5.358
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   379.634
_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  0.667  0.167  0.509  1.0
  Ba  Ba1  1  0.833  0.667  0.491  1.0
  Ba  Ba2  1  0.167  0.333  0.491  1.0
  Ba  Ba3  1  0.333  0.833  0.509  1.0
  Cu  Cu4  1  0.500  0.500  0.000  1.0
  Cu  Cu5  1  0.000  0.000  0.000  1.0
  Si  Si6  1  0.866  0.366  0.976  1.0
  Si  Si7  1  0.634  0.866  0.024  1.0
  Si  Si8  1  0.366  0.134  0.024  1.0
  Si  Si9  1  0.134  0.634  0.976  1.0
  O  O10  1  0.698  0.421  0.844  1.0
  O  O11  1  0.302  0.579  0.844  1.0
  O  O12  1  0.421  0.302  0.156  1.0
  O  O13  1  0.579  0.698  0.156  1.0
  O  O14  1  0.921  0.198  0.844  1.0
  O  O15  1  0.802  0.921  0.156  1.0
  O  O16  1  0.198  0.079  0.156  1.0
  O  O17  1  0.079  0.802  0.844  1.0
  O  O18  1  0.866  0.366  0.277  1.0
  O  O19  1  0.634  0.866  0.723  1.0
  O  O20  1  0.000  0.500  0.870  1.0
  O  O21  1  0.500  0.000  0.130  1.0
  O  O22  1  0.134  0.634  0.277  1.0
  O  O23  1  0.366  0.134  0.723  1.0
[/CIF]
.