The crystal structure described by BaMn2Si2O7 crystallizes in the monoclinic C2/c space group. Ba(1) is bonded in a 8-coordinate geometry to one O(3), one O(4), one O(5), one O(6), two equivalent O(2), and two equivalent O(7) atoms. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(4) and two equivalent O(6) atoms to form MnO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Mn(3)O5 trigonal bipyramids. In the second Mn site, Mn(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. In the third Mn site, Mn(3) is bonded to one O(1), one O(4), one O(7), and two equivalent O(3) atoms to form distorted MnO5 trigonal bipyramids that share  a cornercorner with one Mn(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Si(2)O4 tetrahedra, and  an edgeedge with one Mn(3)O5 trigonal bipyramid. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Mn(3)O5 trigonal bipyramids. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Mn(3)O5 trigonal bipyramid, and  an edgeedge with one Mn(3)O5 trigonal bipyramid. 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 Mn(3), and one Si(1) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to one Mn(2), one Mn(3), and one Si(1) atom. In the third O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Mn(2), and one Si(2) atom. In the fourth O site, O(6) is bonded in a 4-coordinate geometry to one Ba(1), one Mn(1), one Mn(2), and one Si(1) atom. In the fifth O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Mn(3), and one Si(2) atom. In the sixth O site, O(4) is bonded in a 4-coordinate geometry to one Ba(1), one Mn(1), one Mn(3), and one Si(2) atom. In the seventh O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one Si(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_BaMn2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.537
_cell_length_b   7.537
_cell_length_c   14.229
_cell_angle_alpha   89.711
_cell_angle_beta   89.711
_cell_angle_gamma   120.857
_symmetry_Int_Tables_number   1
_cell_volume   693.870
_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  0.281  0.311  0.122  1.0
  Ba  Ba1  1  0.689  0.719  0.378  1.0
  Ba  Ba2  1  0.719  0.689  0.878  1.0
  Ba  Ba3  1  0.311  0.281  0.622  1.0
  Mn  Mn4  1  0.733  0.267  0.250  1.0
  Mn  Mn5  1  0.267  0.733  0.750  1.0
  Mn  Mn6  1  0.270  0.730  0.250  1.0
  Mn  Mn7  1  0.730  0.270  0.750  1.0
  Mn  Mn8  1  0.233  0.700  0.509  1.0
  Mn  Mn9  1  0.300  0.767  0.991  1.0
  Mn  Mn10  1  0.767  0.300  0.491  1.0
  Mn  Mn11  1  0.700  0.233  0.009  1.0
  Si  Si12  1  0.907  0.660  0.135  1.0
  Si  Si13  1  0.340  0.093  0.365  1.0
  Si  Si14  1  0.093  0.340  0.865  1.0
  Si  Si15  1  0.660  0.907  0.635  1.0
  Si  Si16  1  0.075  0.277  0.381  1.0
  Si  Si17  1  0.723  0.925  0.119  1.0
  Si  Si18  1  0.925  0.723  0.619  1.0
  Si  Si19  1  0.277  0.075  0.881  1.0
  O  O20  1  0.135  0.691  0.115  1.0
  O  O21  1  0.309  0.865  0.385  1.0
  O  O22  1  0.865  0.309  0.885  1.0
  O  O23  1  0.691  0.135  0.615  1.0
  O  O24  1  0.216  0.441  0.299  1.0
  O  O25  1  0.559  0.784  0.201  1.0
  O  O26  1  0.784  0.559  0.701  1.0
  O  O27  1  0.441  0.216  0.799  1.0
  O  O28  1  0.885  0.619  0.515  1.0
  O  O29  1  0.381  0.115  0.985  1.0
  O  O30  1  0.115  0.381  0.485  1.0
  O  O31  1  0.619  0.885  0.015  1.0
  O  O32  1  0.833  0.177  0.133  1.0
  O  O33  1  0.823  0.167  0.367  1.0
  O  O34  1  0.167  0.823  0.867  1.0
  O  O35  1  0.177  0.833  0.633  1.0
  O  O36  1  0.926  0.891  0.121  1.0
  O  O37  1  0.109  0.074  0.379  1.0
  O  O38  1  0.074  0.109  0.879  1.0
  O  O39  1  0.891  0.926  0.621  1.0
  O  O40  1  0.854  0.586  0.246  1.0
  O  O41  1  0.414  0.146  0.254  1.0
  O  O42  1  0.146  0.414  0.754  1.0
  O  O43  1  0.586  0.854  0.746  1.0
  O  O44  1  0.728  0.506  0.061  1.0
  O  O45  1  0.494  0.272  0.439  1.0
  O  O46  1  0.272  0.494  0.939  1.0
  O  O47  1  0.506  0.728  0.561  1.0
[/CIF]
.
The crystal structure described by BaMn2Si2O7 crystallizes in the monoclinic C2/c space group. Ba(1) is bonded in a 8-coordinate geometry to one O(3), one O(4), one O(5), one O(6), two equivalent O(2), and two equivalent O(7) atoms. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(4) and two equivalent O(6) atoms to form MnO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Mn(3)O5 trigonal bipyramids. In the second Mn site, Mn(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. In the third Mn site, Mn(3) is bonded to one O(1), one O(4), one O(7), and two equivalent O(3) atoms to form distorted MnO5 trigonal bipyramids that share  a cornercorner with one Mn(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra,  an edgeedge with one Si(2)O4 tetrahedra, and  an edgeedge with one Mn(3)O5 trigonal bipyramid. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Mn(3)O5 trigonal bipyramids. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Mn(3)O5 trigonal bipyramid, and  an edgeedge with one Mn(3)O5 trigonal bipyramid. 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 Mn(3), and one Si(1) atom. In the second O site, O(1) is bonded in a distorted trigonal planar geometry to one Mn(2), one Mn(3), and one Si(1) atom. In the third O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Mn(2), and one Si(2) atom. In the fourth O site, O(6) is bonded in a 4-coordinate geometry to one Ba(1), one Mn(1), one Mn(2), and one Si(1) atom. In the fifth O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Mn(3), and one Si(2) atom. In the sixth O site, O(4) is bonded in a 4-coordinate geometry to one Ba(1), one Mn(1), one Mn(3), and one Si(2) atom. In the seventh O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Ba(1), one Si(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_BaMn2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.537
_cell_length_b   7.537
_cell_length_c   14.229
_cell_angle_alpha   89.711
_cell_angle_beta   89.711
_cell_angle_gamma   120.857
_symmetry_Int_Tables_number   1
_cell_volume   693.870
_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  0.281  0.311  0.122  1.0
  Ba  Ba1  1  0.689  0.719  0.378  1.0
  Ba  Ba2  1  0.719  0.689  0.878  1.0
  Ba  Ba3  1  0.311  0.281  0.622  1.0
  Mn  Mn4  1  0.733  0.267  0.250  1.0
  Mn  Mn5  1  0.267  0.733  0.750  1.0
  Mn  Mn6  1  0.270  0.730  0.250  1.0
  Mn  Mn7  1  0.730  0.270  0.750  1.0
  Mn  Mn8  1  0.233  0.700  0.509  1.0
  Mn  Mn9  1  0.300  0.767  0.991  1.0
  Mn  Mn10  1  0.767  0.300  0.491  1.0
  Mn  Mn11  1  0.700  0.233  0.009  1.0
  Si  Si12  1  0.907  0.660  0.135  1.0
  Si  Si13  1  0.340  0.093  0.365  1.0
  Si  Si14  1  0.093  0.340  0.865  1.0
  Si  Si15  1  0.660  0.907  0.635  1.0
  Si  Si16  1  0.075  0.277  0.381  1.0
  Si  Si17  1  0.723  0.925  0.119  1.0
  Si  Si18  1  0.925  0.723  0.619  1.0
  Si  Si19  1  0.277  0.075  0.881  1.0
  O  O20  1  0.135  0.691  0.115  1.0
  O  O21  1  0.309  0.865  0.385  1.0
  O  O22  1  0.865  0.309  0.885  1.0
  O  O23  1  0.691  0.135  0.615  1.0
  O  O24  1  0.216  0.441  0.299  1.0
  O  O25  1  0.559  0.784  0.201  1.0
  O  O26  1  0.784  0.559  0.701  1.0
  O  O27  1  0.441  0.216  0.799  1.0
  O  O28  1  0.885  0.619  0.515  1.0
  O  O29  1  0.381  0.115  0.985  1.0
  O  O30  1  0.115  0.381  0.485  1.0
  O  O31  1  0.619  0.885  0.015  1.0
  O  O32  1  0.833  0.177  0.133  1.0
  O  O33  1  0.823  0.167  0.367  1.0
  O  O34  1  0.167  0.823  0.867  1.0
  O  O35  1  0.177  0.833  0.633  1.0
  O  O36  1  0.926  0.891  0.121  1.0
  O  O37  1  0.109  0.074  0.379  1.0
  O  O38  1  0.074  0.109  0.879  1.0
  O  O39  1  0.891  0.926  0.621  1.0
  O  O40  1  0.854  0.586  0.246  1.0
  O  O41  1  0.414  0.146  0.254  1.0
  O  O42  1  0.146  0.414  0.754  1.0
  O  O43  1  0.586  0.854  0.746  1.0
  O  O44  1  0.728  0.506  0.061  1.0
  O  O45  1  0.494  0.272  0.439  1.0
  O  O46  1  0.272  0.494  0.939  1.0
  O  O47  1  0.506  0.728  0.561  1.0
[/CIF]
.