The compound described by BaCo2Si2O7 crystallizes in the monoclinic C2/c space group. Ba(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(5), two equivalent O(1), and two equivalent O(7) atoms. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(4), one O(6), and two equivalent O(5) atoms to form distorted CoO5 trigonal bipyramids that share  a cornercorner with one Co(2)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one Si(1)O4 tetrahedra, and  an edgeedge with one Co(1)O5 trigonal bipyramid. In the second Co site, Co(2) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form CoO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Co(1)O5 trigonal bipyramids. In the third Co site, Co(3) is bonded in a 4-coordinate geometry to two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Co(1)O5 trigonal bipyramid, and  an edgeedge with one Co(1)O5 trigonal bipyramid. 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 SiO4 tetrahedra that share  a cornercorner with one Co(2)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Co(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Co(3), and one Si(1) atom. In the second O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Co(1), and one Si(2) atom. In the third O site, O(2) is bonded in a 4-coordinate geometry to one Ba(1), one Co(2), one Co(3), and one Si(2) atom. In the fourth O site, O(6) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one Si(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one Si(1), and one Si(2) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(1), one Co(1), one Co(2), and one Si(1) atom. In the seventh O site, O(5) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Co(1), and one Si(1) atom. is represented by the CIF card [CIF]
data_BaCo2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.433
_cell_length_b   7.433
_cell_length_c   13.926
_cell_angle_alpha   89.941
_cell_angle_beta   89.941
_cell_angle_gamma   120.712
_symmetry_Int_Tables_number   1
_cell_volume   661.523
_cell_formula_units_Z   4
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  0.220  0.182  0.877  1.0
  Ba  Ba1  1  0.818  0.780  0.623  1.0
  Ba  Ba2  1  0.780  0.818  0.123  1.0
  Ba  Ba3  1  0.182  0.220  0.377  1.0
  Co  Co4  1  0.262  0.801  0.490  1.0
  Co  Co5  1  0.199  0.738  0.010  1.0
  Co  Co6  1  0.228  0.772  0.250  1.0
  Co  Co7  1  0.801  0.262  0.990  1.0
  Co  Co8  1  0.233  0.767  0.750  1.0
  Co  Co9  1  0.767  0.233  0.250  1.0
  Co  Co10  1  0.772  0.228  0.750  1.0
  Co  Co11  1  0.738  0.199  0.510  1.0
  Si  Si12  1  0.426  0.212  0.619  1.0
  Si  Si13  1  0.788  0.574  0.881  1.0
  Si  Si14  1  0.574  0.788  0.381  1.0
  Si  Si15  1  0.212  0.426  0.119  1.0
  Si  Si16  1  0.166  0.412  0.633  1.0
  Si  Si17  1  0.588  0.834  0.867  1.0
  Si  Si18  1  0.834  0.588  0.367  1.0
  Si  Si19  1  0.412  0.166  0.133  1.0
  O  O20  1  0.013  0.238  0.554  1.0
  O  O21  1  0.762  0.987  0.946  1.0
  O  O22  1  0.987  0.762  0.446  1.0
  O  O23  1  0.238  0.013  0.054  1.0
  O  O24  1  0.081  0.352  0.744  1.0
  O  O25  1  0.648  0.919  0.756  1.0
  O  O26  1  0.919  0.648  0.256  1.0
  O  O27  1  0.352  0.081  0.244  1.0
  O  O28  1  0.396  0.421  0.622  1.0
  O  O29  1  0.579  0.604  0.878  1.0
  O  O30  1  0.604  0.579  0.378  1.0
  O  O31  1  0.421  0.396  0.122  1.0
  O  O32  1  0.682  0.317  0.634  1.0
  O  O33  1  0.683  0.318  0.866  1.0
  O  O34  1  0.318  0.683  0.366  1.0
  O  O35  1  0.317  0.682  0.134  1.0
  O  O36  1  0.384  0.111  0.511  1.0
  O  O37  1  0.889  0.616  0.989  1.0
  O  O38  1  0.616  0.889  0.489  1.0
  O  O39  1  0.111  0.384  0.011  1.0
  O  O40  1  0.650  0.208  0.115  1.0
  O  O41  1  0.792  0.350  0.385  1.0
  O  O42  1  0.350  0.792  0.885  1.0
  O  O43  1  0.208  0.650  0.615  1.0
  O  O44  1  0.281  0.050  0.702  1.0
  O  O45  1  0.719  0.950  0.298  1.0
  O  O46  1  0.950  0.719  0.798  1.0
  O  O47  1  0.050  0.281  0.202  1.0
[/CIF]
.
The compound described by BaCo2Si2O7 crystallizes in the monoclinic C2/c space group. Ba(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(4), one O(5), two equivalent O(1), and two equivalent O(7) atoms. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(4), one O(6), and two equivalent O(5) atoms to form distorted CoO5 trigonal bipyramids that share  a cornercorner with one Co(2)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one Si(1)O4 tetrahedra, and  an edgeedge with one Co(1)O5 trigonal bipyramid. In the second Co site, Co(2) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form CoO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Co(1)O5 trigonal bipyramids. In the third Co site, Co(3) is bonded in a 4-coordinate geometry to two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Co(1)O5 trigonal bipyramid, and  an edgeedge with one Co(1)O5 trigonal bipyramid. 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 SiO4 tetrahedra that share  a cornercorner with one Co(2)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Co(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Co(3), and one Si(1) atom. In the second O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Co(1), and one Si(2) atom. In the third O site, O(2) is bonded in a 4-coordinate geometry to one Ba(1), one Co(2), one Co(3), and one Si(2) atom. In the fourth O site, O(6) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one Si(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one Si(1), and one Si(2) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(1), one Co(1), one Co(2), and one Si(1) atom. In the seventh O site, O(5) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Co(1), and one Si(1) atom. is represented by the CIF card [CIF]
data_BaCo2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.433
_cell_length_b   7.433
_cell_length_c   13.926
_cell_angle_alpha   89.941
_cell_angle_beta   89.941
_cell_angle_gamma   120.712
_symmetry_Int_Tables_number   1
_cell_volume   661.523
_cell_formula_units_Z   4
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  0.220  0.182  0.877  1.0
  Ba  Ba1  1  0.818  0.780  0.623  1.0
  Ba  Ba2  1  0.780  0.818  0.123  1.0
  Ba  Ba3  1  0.182  0.220  0.377  1.0
  Co  Co4  1  0.262  0.801  0.490  1.0
  Co  Co5  1  0.199  0.738  0.010  1.0
  Co  Co6  1  0.228  0.772  0.250  1.0
  Co  Co7  1  0.801  0.262  0.990  1.0
  Co  Co8  1  0.233  0.767  0.750  1.0
  Co  Co9  1  0.767  0.233  0.250  1.0
  Co  Co10  1  0.772  0.228  0.750  1.0
  Co  Co11  1  0.738  0.199  0.510  1.0
  Si  Si12  1  0.426  0.212  0.619  1.0
  Si  Si13  1  0.788  0.574  0.881  1.0
  Si  Si14  1  0.574  0.788  0.381  1.0
  Si  Si15  1  0.212  0.426  0.119  1.0
  Si  Si16  1  0.166  0.412  0.633  1.0
  Si  Si17  1  0.588  0.834  0.867  1.0
  Si  Si18  1  0.834  0.588  0.367  1.0
  Si  Si19  1  0.412  0.166  0.133  1.0
  O  O20  1  0.013  0.238  0.554  1.0
  O  O21  1  0.762  0.987  0.946  1.0
  O  O22  1  0.987  0.762  0.446  1.0
  O  O23  1  0.238  0.013  0.054  1.0
  O  O24  1  0.081  0.352  0.744  1.0
  O  O25  1  0.648  0.919  0.756  1.0
  O  O26  1  0.919  0.648  0.256  1.0
  O  O27  1  0.352  0.081  0.244  1.0
  O  O28  1  0.396  0.421  0.622  1.0
  O  O29  1  0.579  0.604  0.878  1.0
  O  O30  1  0.604  0.579  0.378  1.0
  O  O31  1  0.421  0.396  0.122  1.0
  O  O32  1  0.682  0.317  0.634  1.0
  O  O33  1  0.683  0.318  0.866  1.0
  O  O34  1  0.318  0.683  0.366  1.0
  O  O35  1  0.317  0.682  0.134  1.0
  O  O36  1  0.384  0.111  0.511  1.0
  O  O37  1  0.889  0.616  0.989  1.0
  O  O38  1  0.616  0.889  0.489  1.0
  O  O39  1  0.111  0.384  0.011  1.0
  O  O40  1  0.650  0.208  0.115  1.0
  O  O41  1  0.792  0.350  0.385  1.0
  O  O42  1  0.350  0.792  0.885  1.0
  O  O43  1  0.208  0.650  0.615  1.0
  O  O44  1  0.281  0.050  0.702  1.0
  O  O45  1  0.719  0.950  0.298  1.0
  O  O46  1  0.950  0.719  0.798  1.0
  O  O47  1  0.050  0.281  0.202  1.0
[/CIF]
.