The crystal structure described by Na2CaFe2(PO4)3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to two equivalent O(3) and four equivalent O(5) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(2) atoms. Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms. Fe(1) is bonded to one O(1), one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and  an edgeedge with one Fe(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-53°. In the second P site, P(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-55°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(2), one Fe(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ca(1), and one P(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Ca(1), one Fe(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Fe(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Fe(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1), one Fe(1), and one P(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2CaFe2(PO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.889
_cell_length_b   8.889
_cell_length_c   6.615
_cell_angle_alpha   73.055
_cell_angle_beta   73.055
_cell_angle_gamma   91.975
_symmetry_Int_Tables_number   1
_cell_volume   474.168
_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  0.975  0.025  0.250  1.0
  Na  Na1  1  0.025  0.975  0.750  1.0
  Na  Na2  1  0.500  0.500  0.000  1.0
  Na  Na3  1  0.500  0.500  0.500  1.0
  Ca  Ca4  1  0.269  0.731  0.250  1.0
  Ca  Ca5  1  0.731  0.269  0.750  1.0
  Fe  Fe6  1  0.388  0.064  0.367  1.0
  Fe  Fe7  1  0.612  0.936  0.633  1.0
  Fe  Fe8  1  0.936  0.612  0.133  1.0
  Fe  Fe9  1  0.064  0.388  0.867  1.0
  P  P10  1  0.719  0.281  0.250  1.0
  P  P11  1  0.281  0.719  0.750  1.0
  P  P12  1  0.659  0.864  0.125  1.0
  P  P13  1  0.341  0.136  0.875  1.0
  P  P14  1  0.136  0.341  0.375  1.0
  P  P15  1  0.864  0.659  0.625  1.0
  O  O16  1  0.551  0.259  0.228  1.0
  O  O17  1  0.449  0.741  0.772  1.0
  O  O18  1  0.741  0.449  0.272  1.0
  O  O19  1  0.259  0.551  0.728  1.0
  O  O20  1  0.541  0.717  0.180  1.0
  O  O21  1  0.459  0.283  0.820  1.0
  O  O22  1  0.283  0.459  0.320  1.0
  O  O23  1  0.717  0.541  0.680  1.0
  O  O24  1  0.739  0.159  0.460  1.0
  O  O25  1  0.261  0.841  0.540  1.0
  O  O26  1  0.841  0.261  0.040  1.0
  O  O27  1  0.159  0.739  0.960  1.0
  O  O28  1  0.602  0.945  0.312  1.0
  O  O29  1  0.398  0.055  0.688  1.0
  O  O30  1  0.055  0.398  0.188  1.0
  O  O31  1  0.945  0.602  0.812  1.0
  O  O32  1  0.831  0.824  0.108  1.0
  O  O33  1  0.169  0.176  0.892  1.0
  O  O34  1  0.176  0.169  0.392  1.0
  O  O35  1  0.824  0.831  0.608  1.0
  O  O36  1  0.333  0.011  0.102  1.0
  O  O37  1  0.667  0.989  0.898  1.0
  O  O38  1  0.989  0.667  0.398  1.0
  O  O39  1  0.011  0.333  0.602  1.0
[/CIF]
.
The crystal structure described by Na2CaFe2(PO4)3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to two equivalent O(3) and four equivalent O(5) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(2) atoms. Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms. Fe(1) is bonded to one O(1), one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and  an edgeedge with one Fe(1)O6 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-53°. In the second P site, P(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-55°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(2), one Fe(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(2), one Ca(1), and one P(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Ca(1), one Fe(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Fe(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Fe(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1), one Fe(1), and one P(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2CaFe2(PO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.889
_cell_length_b   8.889
_cell_length_c   6.615
_cell_angle_alpha   73.055
_cell_angle_beta   73.055
_cell_angle_gamma   91.975
_symmetry_Int_Tables_number   1
_cell_volume   474.168
_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  0.975  0.025  0.250  1.0
  Na  Na1  1  0.025  0.975  0.750  1.0
  Na  Na2  1  0.500  0.500  0.000  1.0
  Na  Na3  1  0.500  0.500  0.500  1.0
  Ca  Ca4  1  0.269  0.731  0.250  1.0
  Ca  Ca5  1  0.731  0.269  0.750  1.0
  Fe  Fe6  1  0.388  0.064  0.367  1.0
  Fe  Fe7  1  0.612  0.936  0.633  1.0
  Fe  Fe8  1  0.936  0.612  0.133  1.0
  Fe  Fe9  1  0.064  0.388  0.867  1.0
  P  P10  1  0.719  0.281  0.250  1.0
  P  P11  1  0.281  0.719  0.750  1.0
  P  P12  1  0.659  0.864  0.125  1.0
  P  P13  1  0.341  0.136  0.875  1.0
  P  P14  1  0.136  0.341  0.375  1.0
  P  P15  1  0.864  0.659  0.625  1.0
  O  O16  1  0.551  0.259  0.228  1.0
  O  O17  1  0.449  0.741  0.772  1.0
  O  O18  1  0.741  0.449  0.272  1.0
  O  O19  1  0.259  0.551  0.728  1.0
  O  O20  1  0.541  0.717  0.180  1.0
  O  O21  1  0.459  0.283  0.820  1.0
  O  O22  1  0.283  0.459  0.320  1.0
  O  O23  1  0.717  0.541  0.680  1.0
  O  O24  1  0.739  0.159  0.460  1.0
  O  O25  1  0.261  0.841  0.540  1.0
  O  O26  1  0.841  0.261  0.040  1.0
  O  O27  1  0.159  0.739  0.960  1.0
  O  O28  1  0.602  0.945  0.312  1.0
  O  O29  1  0.398  0.055  0.688  1.0
  O  O30  1  0.055  0.398  0.188  1.0
  O  O31  1  0.945  0.602  0.812  1.0
  O  O32  1  0.831  0.824  0.108  1.0
  O  O33  1  0.169  0.176  0.892  1.0
  O  O34  1  0.176  0.169  0.392  1.0
  O  O35  1  0.824  0.831  0.608  1.0
  O  O36  1  0.333  0.011  0.102  1.0
  O  O37  1  0.667  0.989  0.898  1.0
  O  O38  1  0.989  0.667  0.398  1.0
  O  O39  1  0.011  0.333  0.602  1.0
[/CIF]
.