The structure described by KErP2O9 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. Er(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), one O(7), and one O(9) atom to form distorted ErO7 pentagonal bipyramids that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Er(1)O7 pentagonal bipyramids and  a cornercorner with one P(2)O4 tetrahedra. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Er(1)O7 pentagonal bipyramids and  a cornercorner with one P(1)O4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(5) is bonded in a 2-coordinate geometry to one K(1), one Er(1), and one P(2) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to one K(1), one Er(1), and one P(2) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to one K(1), one Er(1), and one P(2) atom. In the fourth O site, O(8) is bonded in a 2-coordinate geometry to one K(1) and one O(9) atom. In the fifth O site, O(1) is bonded in a 2-coordinate geometry to one K(1), one Er(1), and one P(1) atom. In the sixth O site, O(9) is bonded in a 3-coordinate geometry to one K(1), one Er(1), and one O(8) atom. In the seventh O site, O(2) is bonded in a 3-coordinate geometry to one K(1), one Er(1), and one P(1) atom. In the eighth O site, O(3) is bonded in a 2-coordinate geometry to one K(1), one Er(1), and one P(1) atom. In the ninth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one K(1), one P(1), and one P(2) atom. is represented by the CIF file [CIF]
data_KErP2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.561
_cell_length_b   7.690
_cell_length_c   10.137
_cell_angle_alpha   88.842
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   823.099
_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
  K  K0  1  0.721  0.740  0.146  1.0
  K  K1  1  0.221  0.260  0.354  1.0
  K  K2  1  0.279  0.260  0.854  1.0
  K  K3  1  0.779  0.740  0.646  1.0
  Er  Er4  1  0.622  0.251  0.167  1.0
  Er  Er5  1  0.122  0.749  0.333  1.0
  Er  Er6  1  0.378  0.749  0.833  1.0
  Er  Er7  1  0.878  0.251  0.667  1.0
  P  P8  1  0.393  0.604  0.166  1.0
  P  P9  1  0.893  0.396  0.334  1.0
  P  P10  1  0.607  0.396  0.834  1.0
  P  P11  1  0.107  0.604  0.666  1.0
  P  P12  1  0.647  0.033  0.867  1.0
  P  P13  1  0.147  0.967  0.633  1.0
  P  P14  1  0.353  0.967  0.133  1.0
  P  P15  1  0.853  0.033  0.367  1.0
  O  O16  1  0.361  0.579  0.021  1.0
  O  O17  1  0.861  0.421  0.479  1.0
  O  O18  1  0.639  0.421  0.979  1.0
  O  O19  1  0.139  0.579  0.521  1.0
  O  O20  1  0.282  0.582  0.260  1.0
  O  O21  1  0.782  0.418  0.240  1.0
  O  O22  1  0.718  0.418  0.740  1.0
  O  O23  1  0.218  0.582  0.760  1.0
  O  O24  1  0.508  0.495  0.210  1.0
  O  O25  1  0.008  0.505  0.290  1.0
  O  O26  1  0.492  0.505  0.790  1.0
  O  O27  1  0.992  0.495  0.710  1.0
  O  O28  1  0.445  0.804  0.179  1.0
  O  O29  1  0.945  0.196  0.321  1.0
  O  O30  1  0.555  0.196  0.821  1.0
  O  O31  1  0.055  0.804  0.679  1.0
  O  O32  1  0.572  0.869  0.834  1.0
  O  O33  1  0.072  0.131  0.666  1.0
  O  O34  1  0.428  0.131  0.166  1.0
  O  O35  1  0.928  0.869  0.334  1.0
  O  O36  1  0.769  0.050  0.787  1.0
  O  O37  1  0.269  0.950  0.713  1.0
  O  O38  1  0.231  0.950  0.213  1.0
  O  O39  1  0.731  0.050  0.287  1.0
  O  O40  1  0.668  0.050  0.016  1.0
  O  O41  1  0.168  0.950  0.484  1.0
  O  O42  1  0.332  0.950  0.984  1.0
  O  O43  1  0.832  0.050  0.516  1.0
  O  O44  1  0.931  0.585  0.957  1.0
  O  O45  1  0.431  0.415  0.543  1.0
  O  O46  1  0.069  0.415  0.043  1.0
  O  O47  1  0.569  0.585  0.457  1.0
  O  O48  1  0.522  0.297  0.394  1.0
  O  O49  1  0.022  0.703  0.106  1.0
  O  O50  1  0.478  0.703  0.606  1.0
  O  O51  1  0.978  0.297  0.894  1.0
[/CIF]
.
The structure described by KErP2O9 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. Er(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), one O(7), and one O(9) atom to form distorted ErO7 pentagonal bipyramids that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Er(1)O7 pentagonal bipyramids and  a cornercorner with one P(2)O4 tetrahedra. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Er(1)O7 pentagonal bipyramids and  a cornercorner with one P(1)O4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(5) is bonded in a 2-coordinate geometry to one K(1), one Er(1), and one P(2) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to one K(1), one Er(1), and one P(2) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to one K(1), one Er(1), and one P(2) atom. In the fourth O site, O(8) is bonded in a 2-coordinate geometry to one K(1) and one O(9) atom. In the fifth O site, O(1) is bonded in a 2-coordinate geometry to one K(1), one Er(1), and one P(1) atom. In the sixth O site, O(9) is bonded in a 3-coordinate geometry to one K(1), one Er(1), and one O(8) atom. In the seventh O site, O(2) is bonded in a 3-coordinate geometry to one K(1), one Er(1), and one P(1) atom. In the eighth O site, O(3) is bonded in a 2-coordinate geometry to one K(1), one Er(1), and one P(1) atom. In the ninth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one K(1), one P(1), and one P(2) atom. is represented by the CIF file [CIF]
data_KErP2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.561
_cell_length_b   7.690
_cell_length_c   10.137
_cell_angle_alpha   88.842
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   823.099
_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
  K  K0  1  0.721  0.740  0.146  1.0
  K  K1  1  0.221  0.260  0.354  1.0
  K  K2  1  0.279  0.260  0.854  1.0
  K  K3  1  0.779  0.740  0.646  1.0
  Er  Er4  1  0.622  0.251  0.167  1.0
  Er  Er5  1  0.122  0.749  0.333  1.0
  Er  Er6  1  0.378  0.749  0.833  1.0
  Er  Er7  1  0.878  0.251  0.667  1.0
  P  P8  1  0.393  0.604  0.166  1.0
  P  P9  1  0.893  0.396  0.334  1.0
  P  P10  1  0.607  0.396  0.834  1.0
  P  P11  1  0.107  0.604  0.666  1.0
  P  P12  1  0.647  0.033  0.867  1.0
  P  P13  1  0.147  0.967  0.633  1.0
  P  P14  1  0.353  0.967  0.133  1.0
  P  P15  1  0.853  0.033  0.367  1.0
  O  O16  1  0.361  0.579  0.021  1.0
  O  O17  1  0.861  0.421  0.479  1.0
  O  O18  1  0.639  0.421  0.979  1.0
  O  O19  1  0.139  0.579  0.521  1.0
  O  O20  1  0.282  0.582  0.260  1.0
  O  O21  1  0.782  0.418  0.240  1.0
  O  O22  1  0.718  0.418  0.740  1.0
  O  O23  1  0.218  0.582  0.760  1.0
  O  O24  1  0.508  0.495  0.210  1.0
  O  O25  1  0.008  0.505  0.290  1.0
  O  O26  1  0.492  0.505  0.790  1.0
  O  O27  1  0.992  0.495  0.710  1.0
  O  O28  1  0.445  0.804  0.179  1.0
  O  O29  1  0.945  0.196  0.321  1.0
  O  O30  1  0.555  0.196  0.821  1.0
  O  O31  1  0.055  0.804  0.679  1.0
  O  O32  1  0.572  0.869  0.834  1.0
  O  O33  1  0.072  0.131  0.666  1.0
  O  O34  1  0.428  0.131  0.166  1.0
  O  O35  1  0.928  0.869  0.334  1.0
  O  O36  1  0.769  0.050  0.787  1.0
  O  O37  1  0.269  0.950  0.713  1.0
  O  O38  1  0.231  0.950  0.213  1.0
  O  O39  1  0.731  0.050  0.287  1.0
  O  O40  1  0.668  0.050  0.016  1.0
  O  O41  1  0.168  0.950  0.484  1.0
  O  O42  1  0.332  0.950  0.984  1.0
  O  O43  1  0.832  0.050  0.516  1.0
  O  O44  1  0.931  0.585  0.957  1.0
  O  O45  1  0.431  0.415  0.543  1.0
  O  O46  1  0.069  0.415  0.043  1.0
  O  O47  1  0.569  0.585  0.457  1.0
  O  O48  1  0.522  0.297  0.394  1.0
  O  O49  1  0.022  0.703  0.106  1.0
  O  O50  1  0.478  0.703  0.606  1.0
  O  O51  1  0.978  0.297  0.894  1.0
[/CIF]
.