The material described by BaAs2O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(10), one O(14), one O(16), one O(17), one O(3), one O(4), one O(5), one O(8), and one O(9) atom. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(11), one O(14), one O(15), one O(17), one O(2), one O(3), one O(6), one O(7), and one O(9) atom. There are four inequivalent As sites. In the first As site, As(1) is bonded in a trigonal planar geometry to one O(2), one O(3), and one O(4) atom. In the second As site, As(2) is bonded in a tetrahedral geometry to one O(5), one O(6), one O(7), and one O(8) atom. In the third As site, As(3) is bonded in a tetrahedral geometry to one O(10), one O(11), one O(12), and one O(9) atom. In the fourth As site, As(4) is bonded in a tetrahedral geometry to one O(13), one O(14), one O(15), and one O(16) atom. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one O(18) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Ba(2) and one As(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one As(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Ba(1) and one As(1) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Ba(1) and one As(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ba(2) and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Ba(2) and one As(2) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one As(3) atom. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one Ba(1) and one As(3) atom. In the eleventh O site, O(11) is bonded in a distorted single-bond geometry to one Ba(2) and one As(3) atom. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one As(3) and one O(18) atom. In the thirteenth O site, O(13) is bonded in a single-bond geometry to one As(4) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one As(4) atom. In the fifteenth O site, O(15) is bonded in a 2-coordinate geometry to one Ba(2) and one As(4) atom. In the sixteenth O site, O(16) is bonded in a single-bond geometry to one Ba(1) and one As(4) atom. In the seventeenth O site, O(17) is bonded in a bent 150 degrees geometry to one Ba(1) and one Ba(2) atom. In the eighteenth O site, O(18) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(12) atom. is represented by the CIF file [CIF]
data_BaAs2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.573
_cell_length_b   9.698
_cell_length_c   12.221
_cell_angle_alpha   73.830
_cell_angle_beta   63.921
_cell_angle_gamma   66.110
_symmetry_Int_Tables_number   1
_cell_volume   828.180
_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  0.196  0.954  0.738  1.0
  Ba  Ba1  1  0.804  0.046  0.262  1.0
  Ba  Ba2  1  0.650  0.457  0.756  1.0
  Ba  Ba3  1  0.350  0.543  0.244  1.0
  As  As4  1  0.478  0.762  0.457  1.0
  As  As5  1  0.522  0.238  0.543  1.0
  As  As6  1  0.952  0.749  0.556  1.0
  As  As7  1  0.048  0.251  0.444  1.0
  As  As8  1  0.960  0.292  0.934  1.0
  As  As9  1  0.040  0.708  0.066  1.0
  As  As10  1  0.483  0.830  0.929  1.0
  As  As11  1  0.517  0.170  0.071  1.0
  O  O12  1  0.782  0.566  0.321  1.0
  O  O13  1  0.218  0.434  0.679  1.0
  O  O14  1  0.372  0.685  0.413  1.0
  O  O15  1  0.628  0.315  0.587  1.0
  O  O16  1  0.484  0.708  0.597  1.0
  O  O17  1  0.516  0.292  0.403  1.0
  O  O18  1  0.551  0.903  0.368  1.0
  O  O19  1  0.449  0.097  0.632  1.0
  O  O20  1  0.122  0.754  0.596  1.0
  O  O21  1  0.878  0.246  0.404  1.0
  O  O22  1  0.806  0.685  0.694  1.0
  O  O23  1  0.194  0.315  0.306  1.0
  O  O24  1  0.039  0.612  0.458  1.0
  O  O25  1  0.961  0.388  0.542  1.0
  O  O26  1  0.862  0.914  0.478  1.0
  O  O27  1  0.138  0.086  0.522  1.0
  O  O28  1  0.009  0.248  0.793  1.0
  O  O29  1  0.991  0.752  0.207  1.0
  O  O30  1  0.005  0.147  0.042  1.0
  O  O31  1  0.995  0.853  0.958  1.0
  O  O32  1  0.735  0.417  0.983  1.0
  O  O33  1  0.265  0.583  0.017  1.0
  O  O34  1  0.103  0.401  0.911  1.0
  O  O35  1  0.897  0.599  0.089  1.0
  O  O36  1  0.708  0.832  0.836  1.0
  O  O37  1  0.292  0.168  0.164  1.0
  O  O38  1  0.427  0.722  0.866  1.0
  O  O39  1  0.573  0.278  0.134  1.0
  O  O40  1  0.449  0.772  0.079  1.0
  O  O41  1  0.551  0.228  0.921  1.0
  O  O42  1  0.357  0.017  0.894  1.0
  O  O43  1  0.643  0.983  0.106  1.0
  O  O44  1  0.849  0.149  0.747  1.0
  O  O45  1  0.151  0.851  0.253  1.0
  O  O46  1  0.233  0.456  0.768  1.0
  O  O47  1  0.767  0.544  0.232  1.0
[/CIF]
.
The material described by BaAs2O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(10), one O(14), one O(16), one O(17), one O(3), one O(4), one O(5), one O(8), and one O(9) atom. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(11), one O(14), one O(15), one O(17), one O(2), one O(3), one O(6), one O(7), and one O(9) atom. There are four inequivalent As sites. In the first As site, As(1) is bonded in a trigonal planar geometry to one O(2), one O(3), and one O(4) atom. In the second As site, As(2) is bonded in a tetrahedral geometry to one O(5), one O(6), one O(7), and one O(8) atom. In the third As site, As(3) is bonded in a tetrahedral geometry to one O(10), one O(11), one O(12), and one O(9) atom. In the fourth As site, As(4) is bonded in a tetrahedral geometry to one O(13), one O(14), one O(15), and one O(16) atom. There are eighteen inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one O(18) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Ba(2) and one As(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one As(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Ba(1) and one As(1) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Ba(1) and one As(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ba(2) and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Ba(2) and one As(2) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one As(3) atom. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one Ba(1) and one As(3) atom. In the eleventh O site, O(11) is bonded in a distorted single-bond geometry to one Ba(2) and one As(3) atom. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one As(3) and one O(18) atom. In the thirteenth O site, O(13) is bonded in a single-bond geometry to one As(4) atom. In the fourteenth O site, O(14) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one As(4) atom. In the fifteenth O site, O(15) is bonded in a 2-coordinate geometry to one Ba(2) and one As(4) atom. In the sixteenth O site, O(16) is bonded in a single-bond geometry to one Ba(1) and one As(4) atom. In the seventeenth O site, O(17) is bonded in a bent 150 degrees geometry to one Ba(1) and one Ba(2) atom. In the eighteenth O site, O(18) is bonded in a distorted bent 120 degrees geometry to one O(1) and one O(12) atom. is represented by the CIF file [CIF]
data_BaAs2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.573
_cell_length_b   9.698
_cell_length_c   12.221
_cell_angle_alpha   73.830
_cell_angle_beta   63.921
_cell_angle_gamma   66.110
_symmetry_Int_Tables_number   1
_cell_volume   828.180
_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  0.196  0.954  0.738  1.0
  Ba  Ba1  1  0.804  0.046  0.262  1.0
  Ba  Ba2  1  0.650  0.457  0.756  1.0
  Ba  Ba3  1  0.350  0.543  0.244  1.0
  As  As4  1  0.478  0.762  0.457  1.0
  As  As5  1  0.522  0.238  0.543  1.0
  As  As6  1  0.952  0.749  0.556  1.0
  As  As7  1  0.048  0.251  0.444  1.0
  As  As8  1  0.960  0.292  0.934  1.0
  As  As9  1  0.040  0.708  0.066  1.0
  As  As10  1  0.483  0.830  0.929  1.0
  As  As11  1  0.517  0.170  0.071  1.0
  O  O12  1  0.782  0.566  0.321  1.0
  O  O13  1  0.218  0.434  0.679  1.0
  O  O14  1  0.372  0.685  0.413  1.0
  O  O15  1  0.628  0.315  0.587  1.0
  O  O16  1  0.484  0.708  0.597  1.0
  O  O17  1  0.516  0.292  0.403  1.0
  O  O18  1  0.551  0.903  0.368  1.0
  O  O19  1  0.449  0.097  0.632  1.0
  O  O20  1  0.122  0.754  0.596  1.0
  O  O21  1  0.878  0.246  0.404  1.0
  O  O22  1  0.806  0.685  0.694  1.0
  O  O23  1  0.194  0.315  0.306  1.0
  O  O24  1  0.039  0.612  0.458  1.0
  O  O25  1  0.961  0.388  0.542  1.0
  O  O26  1  0.862  0.914  0.478  1.0
  O  O27  1  0.138  0.086  0.522  1.0
  O  O28  1  0.009  0.248  0.793  1.0
  O  O29  1  0.991  0.752  0.207  1.0
  O  O30  1  0.005  0.147  0.042  1.0
  O  O31  1  0.995  0.853  0.958  1.0
  O  O32  1  0.735  0.417  0.983  1.0
  O  O33  1  0.265  0.583  0.017  1.0
  O  O34  1  0.103  0.401  0.911  1.0
  O  O35  1  0.897  0.599  0.089  1.0
  O  O36  1  0.708  0.832  0.836  1.0
  O  O37  1  0.292  0.168  0.164  1.0
  O  O38  1  0.427  0.722  0.866  1.0
  O  O39  1  0.573  0.278  0.134  1.0
  O  O40  1  0.449  0.772  0.079  1.0
  O  O41  1  0.551  0.228  0.921  1.0
  O  O42  1  0.357  0.017  0.894  1.0
  O  O43  1  0.643  0.983  0.106  1.0
  O  O44  1  0.849  0.149  0.747  1.0
  O  O45  1  0.151  0.851  0.253  1.0
  O  O46  1  0.233  0.456  0.768  1.0
  O  O47  1  0.767  0.544  0.232  1.0
[/CIF]
.