The crystal structure described by Na4Cr2P4O15 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. In the second Na site, Na(2) is bonded to one O(1), one O(3), one O(4), one O(8), and two equivalent O(7) atoms to form distorted NaO6 pentagonal pyramids that share  a cornercorner with one Na(2)O6 pentagonal pyramid,  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  an edgeedge with one Na(2)O6 pentagonal pyramid, and  an edgeedge with one P(1)O4 tetrahedra. Cr(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(3), one O(5), one O(6), and one O(7) atom. 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  a cornercorner with one Na(2)O6 pentagonal pyramid,  a cornercorner with one P(2)O4 tetrahedra, and  an edgeedge with one Na(2)O6 pentagonal pyramid. In the second P site, P(2) is bonded to one O(2), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Na(2)O6 pentagonal pyramids and  a cornercorner with one P(1)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), and one P(1) atom. In the second O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Cr(1), and one P(2) atom. In the third O site, O(6) is bonded in a 3-coordinate geometry to one Na(1), one Cr(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Na(2), one Cr(1), and one P(2) atom. In the fifth O site, O(8) is bonded in a distorted linear geometry to two equivalent Na(2) atoms. In the sixth O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Cr(1), and one P(1) atom. In the seventh O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one P(1), and one P(2) atom. In the eighth O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Cr(1), and one P(1) atom. is represented by the CIF file [CIF]
data_Na4Cr2P4O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.877
_cell_length_b   7.866
_cell_length_c   10.527
_cell_angle_alpha   54.481
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   665.707
_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
  Na  Na0  1  0.341  0.856  0.680  1.0
  Na  Na1  1  0.159  0.856  0.180  1.0
  Na  Na2  1  0.659  0.144  0.320  1.0
  Na  Na3  1  0.841  0.144  0.820  1.0
  Na  Na4  1  0.535  0.846  0.213  1.0
  Na  Na5  1  0.965  0.846  0.713  1.0
  Na  Na6  1  0.465  0.154  0.787  1.0
  Na  Na7  1  0.035  0.154  0.287  1.0
  Cr  Cr8  1  0.244  0.370  0.947  1.0
  Cr  Cr9  1  0.256  0.370  0.447  1.0
  Cr  Cr10  1  0.756  0.630  0.053  1.0
  Cr  Cr11  1  0.744  0.630  0.553  1.0
  P  P12  1  0.354  0.129  0.300  1.0
  P  P13  1  0.146  0.129  0.800  1.0
  P  P14  1  0.646  0.871  0.700  1.0
  P  P15  1  0.854  0.871  0.200  1.0
  P  P16  1  0.376  0.581  0.103  1.0
  P  P17  1  0.124  0.581  0.603  1.0
  P  P18  1  0.624  0.419  0.897  1.0
  P  P19  1  0.876  0.419  0.397  1.0
  O  O20  1  0.254  0.144  0.180  1.0
  O  O21  1  0.246  0.144  0.680  1.0
  O  O22  1  0.746  0.856  0.820  1.0
  O  O23  1  0.754  0.856  0.320  1.0
  O  O24  1  0.441  0.346  0.210  1.0
  O  O25  1  0.059  0.346  0.710  1.0
  O  O26  1  0.559  0.654  0.790  1.0
  O  O27  1  0.941  0.654  0.290  1.0
  O  O28  1  0.230  0.127  0.925  1.0
  O  O29  1  0.270  0.127  0.425  1.0
  O  O30  1  0.770  0.873  0.075  1.0
  O  O31  1  0.730  0.873  0.575  1.0
  O  O32  1  0.457  0.959  0.362  1.0
  O  O33  1  0.043  0.959  0.862  1.0
  O  O34  1  0.543  0.041  0.638  1.0
  O  O35  1  0.957  0.041  0.138  1.0
  O  O36  1  0.228  0.582  0.712  1.0
  O  O37  1  0.272  0.582  0.212  1.0
  O  O38  1  0.772  0.418  0.288  1.0
  O  O39  1  0.728  0.418  0.788  1.0
  O  O40  1  0.307  0.601  0.964  1.0
  O  O41  1  0.193  0.601  0.464  1.0
  O  O42  1  0.693  0.399  0.036  1.0
  O  O43  1  0.807  0.399  0.536  1.0
  O  O44  1  0.493  0.731  0.056  1.0
  O  O45  1  0.007  0.731  0.556  1.0
  O  O46  1  0.507  0.269  0.944  1.0
  O  O47  1  0.993  0.269  0.444  1.0
  O  O48  1  0.500  0.500  0.500  1.0
  O  O49  1  0.000  0.500  0.000  1.0
[/CIF]
.
The crystal structure described by Na4Cr2P4O15 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. In the second Na site, Na(2) is bonded to one O(1), one O(3), one O(4), one O(8), and two equivalent O(7) atoms to form distorted NaO6 pentagonal pyramids that share  a cornercorner with one Na(2)O6 pentagonal pyramid,  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  an edgeedge with one Na(2)O6 pentagonal pyramid, and  an edgeedge with one P(1)O4 tetrahedra. Cr(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(3), one O(5), one O(6), and one O(7) atom. 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  a cornercorner with one Na(2)O6 pentagonal pyramid,  a cornercorner with one P(2)O4 tetrahedra, and  an edgeedge with one Na(2)O6 pentagonal pyramid. In the second P site, P(2) is bonded to one O(2), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Na(2)O6 pentagonal pyramids and  a cornercorner with one P(1)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Na(2), and one P(1) atom. In the second O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Cr(1), and one P(2) atom. In the third O site, O(6) is bonded in a 3-coordinate geometry to one Na(1), one Cr(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Na(2), one Cr(1), and one P(2) atom. In the fifth O site, O(8) is bonded in a distorted linear geometry to two equivalent Na(2) atoms. In the sixth O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Cr(1), and one P(1) atom. In the seventh O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one P(1), and one P(2) atom. In the eighth O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Cr(1), and one P(1) atom. is represented by the CIF file [CIF]
data_Na4Cr2P4O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.877
_cell_length_b   7.866
_cell_length_c   10.527
_cell_angle_alpha   54.481
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   665.707
_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
  Na  Na0  1  0.341  0.856  0.680  1.0
  Na  Na1  1  0.159  0.856  0.180  1.0
  Na  Na2  1  0.659  0.144  0.320  1.0
  Na  Na3  1  0.841  0.144  0.820  1.0
  Na  Na4  1  0.535  0.846  0.213  1.0
  Na  Na5  1  0.965  0.846  0.713  1.0
  Na  Na6  1  0.465  0.154  0.787  1.0
  Na  Na7  1  0.035  0.154  0.287  1.0
  Cr  Cr8  1  0.244  0.370  0.947  1.0
  Cr  Cr9  1  0.256  0.370  0.447  1.0
  Cr  Cr10  1  0.756  0.630  0.053  1.0
  Cr  Cr11  1  0.744  0.630  0.553  1.0
  P  P12  1  0.354  0.129  0.300  1.0
  P  P13  1  0.146  0.129  0.800  1.0
  P  P14  1  0.646  0.871  0.700  1.0
  P  P15  1  0.854  0.871  0.200  1.0
  P  P16  1  0.376  0.581  0.103  1.0
  P  P17  1  0.124  0.581  0.603  1.0
  P  P18  1  0.624  0.419  0.897  1.0
  P  P19  1  0.876  0.419  0.397  1.0
  O  O20  1  0.254  0.144  0.180  1.0
  O  O21  1  0.246  0.144  0.680  1.0
  O  O22  1  0.746  0.856  0.820  1.0
  O  O23  1  0.754  0.856  0.320  1.0
  O  O24  1  0.441  0.346  0.210  1.0
  O  O25  1  0.059  0.346  0.710  1.0
  O  O26  1  0.559  0.654  0.790  1.0
  O  O27  1  0.941  0.654  0.290  1.0
  O  O28  1  0.230  0.127  0.925  1.0
  O  O29  1  0.270  0.127  0.425  1.0
  O  O30  1  0.770  0.873  0.075  1.0
  O  O31  1  0.730  0.873  0.575  1.0
  O  O32  1  0.457  0.959  0.362  1.0
  O  O33  1  0.043  0.959  0.862  1.0
  O  O34  1  0.543  0.041  0.638  1.0
  O  O35  1  0.957  0.041  0.138  1.0
  O  O36  1  0.228  0.582  0.712  1.0
  O  O37  1  0.272  0.582  0.212  1.0
  O  O38  1  0.772  0.418  0.288  1.0
  O  O39  1  0.728  0.418  0.788  1.0
  O  O40  1  0.307  0.601  0.964  1.0
  O  O41  1  0.193  0.601  0.464  1.0
  O  O42  1  0.693  0.399  0.036  1.0
  O  O43  1  0.807  0.399  0.536  1.0
  O  O44  1  0.493  0.731  0.056  1.0
  O  O45  1  0.007  0.731  0.556  1.0
  O  O46  1  0.507  0.269  0.944  1.0
  O  O47  1  0.993  0.269  0.444  1.0
  O  O48  1  0.500  0.500  0.500  1.0
  O  O49  1  0.000  0.500  0.000  1.0
[/CIF]
.