The compound described by Na2CrAl(P2O7)2 crystallizes in the monoclinic P2_1 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(10), one O(11), one O(13), one O(3), and one O(8) atom. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to one O(12), one O(13), one O(14), one O(2), one O(4), one O(7), and one O(9) atom. Cr(1) is bonded to one O(1), one O(10), one O(11), one O(13), one O(5), and one O(8) atom to form CrO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. Al(1) is bonded to one O(12), one O(14), one O(2), one O(6), one O(7), and one O(9) atom to form AlO6 octahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(4)O4 tetrahedra. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(11), one O(3), one O(5), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Al(1)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 22-52°. In the second P site, P(2) is bonded to one O(10), one O(12), one O(4), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra, corners with two equivalent Al(1)O6 octahedra, and  a cornercorner with one P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 17-48°. In the third P site, P(3) is bonded to one O(1), one O(13), one O(3), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Al(1)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-55°. In the fourth P site, P(4) is bonded to one O(14), one O(2), one O(4), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra, corners with two equivalent Al(1)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-53°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Cr(1), and one P(3) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one P(4) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one P(1), and one P(3) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one P(2), and one P(4) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted linear geometry to one Al(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one P(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Na(1), one Cr(1), and one P(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one P(1) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Na(1), one Cr(1), and one P(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Na(1), one Cr(1), and one P(1) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Na(2), one Al(1), and one P(2) atom. In the thirteenth O site, O(13) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Cr(1), and one P(3) atom. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one P(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2AlCr(P2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.914
_cell_length_b   7.308
_cell_length_c   9.501
_cell_angle_alpha   68.473
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   511.168
_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  0.479  0.710  0.044  1.0
  Na  Na1  1  0.979  0.290  0.956  1.0
  Na  Na2  1  0.521  0.291  0.455  1.0
  Na  Na3  1  0.021  0.709  0.545  1.0
  Al  Al4  1  0.990  0.262  0.501  1.0
  Al  Al5  1  0.490  0.738  0.499  1.0
  Cr  Cr6  1  0.007  0.739  0.997  1.0
  Cr  Cr7  1  0.507  0.261  0.003  1.0
  P  P8  1  0.759  0.078  0.794  1.0
  P  P9  1  0.259  0.922  0.206  1.0
  P  P10  1  0.245  0.928  0.699  1.0
  P  P11  1  0.745  0.072  0.301  1.0
  P  P12  1  0.708  0.674  0.791  1.0
  P  P13  1  0.208  0.326  0.209  1.0
  P  P14  1  0.289  0.330  0.701  1.0
  P  P15  1  0.789  0.670  0.299  1.0
  O  O16  1  0.584  0.537  0.902  1.0
  O  O17  1  0.084  0.463  0.098  1.0
  O  O18  1  0.413  0.475  0.596  1.0
  O  O19  1  0.913  0.525  0.404  1.0
  O  O20  1  0.655  0.882  0.804  1.0
  O  O21  1  0.155  0.118  0.196  1.0
  O  O22  1  0.351  0.123  0.690  1.0
  O  O23  1  0.851  0.877  0.310  1.0
  O  O24  1  0.637  0.191  0.853  1.0
  O  O25  1  0.137  0.809  0.147  1.0
  O  O26  1  0.365  0.818  0.633  1.0
  O  O27  1  0.865  0.182  0.367  1.0
  O  O28  1  0.690  0.688  0.627  1.0
  O  O29  1  0.190  0.312  0.373  1.0
  O  O30  1  0.296  0.315  0.866  1.0
  O  O31  1  0.796  0.685  0.134  1.0
  O  O32  1  0.798  0.195  0.628  1.0
  O  O33  1  0.298  0.805  0.372  1.0
  O  O34  1  0.213  0.805  0.865  1.0
  O  O35  1  0.713  0.195  0.135  1.0
  O  O36  1  0.918  0.012  0.893  1.0
  O  O37  1  0.418  0.988  0.107  1.0
  O  O38  1  0.084  0.999  0.604  1.0
  O  O39  1  0.584  0.001  0.396  1.0
  O  O40  1  0.894  0.637  0.842  1.0
  O  O41  1  0.394  0.363  0.158  1.0
  O  O42  1  0.105  0.360  0.643  1.0
  O  O43  1  0.605  0.640  0.357  1.0
[/CIF]
.
The compound described by Na2CrAl(P2O7)2 crystallizes in the monoclinic P2_1 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(10), one O(11), one O(13), one O(3), and one O(8) atom. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to one O(12), one O(13), one O(14), one O(2), one O(4), one O(7), and one O(9) atom. Cr(1) is bonded to one O(1), one O(10), one O(11), one O(13), one O(5), and one O(8) atom to form CrO6 octahedra that share  a cornercorner with one P(2)O4 tetrahedra,  a cornercorner with one P(4)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. Al(1) is bonded to one O(12), one O(14), one O(2), one O(6), one O(7), and one O(9) atom to form AlO6 octahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(4)O4 tetrahedra. There are four inequivalent P sites. In the first P site, P(1) is bonded to one O(11), one O(3), one O(5), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Al(1)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 22-52°. In the second P site, P(2) is bonded to one O(10), one O(12), one O(4), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra, corners with two equivalent Al(1)O6 octahedra, and  a cornercorner with one P(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 17-48°. In the third P site, P(3) is bonded to one O(1), one O(13), one O(3), and one O(7) atom to form PO4 tetrahedra that share  a cornercorner with one Al(1)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-55°. In the fourth P site, P(4) is bonded to one O(14), one O(2), one O(4), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra, corners with two equivalent Al(1)O6 octahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 31-53°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Cr(1), and one P(3) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one P(4) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one P(1), and one P(3) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one P(2), and one P(4) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Cr(1) and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted linear geometry to one Al(1) and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one P(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Na(1), one Cr(1), and one P(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one P(1) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Na(1), one Cr(1), and one P(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Na(1), one Cr(1), and one P(1) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Na(2), one Al(1), and one P(2) atom. In the thirteenth O site, O(13) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Cr(1), and one P(3) atom. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one P(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2AlCr(P2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.914
_cell_length_b   7.308
_cell_length_c   9.501
_cell_angle_alpha   68.473
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   511.168
_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  0.479  0.710  0.044  1.0
  Na  Na1  1  0.979  0.290  0.956  1.0
  Na  Na2  1  0.521  0.291  0.455  1.0
  Na  Na3  1  0.021  0.709  0.545  1.0
  Al  Al4  1  0.990  0.262  0.501  1.0
  Al  Al5  1  0.490  0.738  0.499  1.0
  Cr  Cr6  1  0.007  0.739  0.997  1.0
  Cr  Cr7  1  0.507  0.261  0.003  1.0
  P  P8  1  0.759  0.078  0.794  1.0
  P  P9  1  0.259  0.922  0.206  1.0
  P  P10  1  0.245  0.928  0.699  1.0
  P  P11  1  0.745  0.072  0.301  1.0
  P  P12  1  0.708  0.674  0.791  1.0
  P  P13  1  0.208  0.326  0.209  1.0
  P  P14  1  0.289  0.330  0.701  1.0
  P  P15  1  0.789  0.670  0.299  1.0
  O  O16  1  0.584  0.537  0.902  1.0
  O  O17  1  0.084  0.463  0.098  1.0
  O  O18  1  0.413  0.475  0.596  1.0
  O  O19  1  0.913  0.525  0.404  1.0
  O  O20  1  0.655  0.882  0.804  1.0
  O  O21  1  0.155  0.118  0.196  1.0
  O  O22  1  0.351  0.123  0.690  1.0
  O  O23  1  0.851  0.877  0.310  1.0
  O  O24  1  0.637  0.191  0.853  1.0
  O  O25  1  0.137  0.809  0.147  1.0
  O  O26  1  0.365  0.818  0.633  1.0
  O  O27  1  0.865  0.182  0.367  1.0
  O  O28  1  0.690  0.688  0.627  1.0
  O  O29  1  0.190  0.312  0.373  1.0
  O  O30  1  0.296  0.315  0.866  1.0
  O  O31  1  0.796  0.685  0.134  1.0
  O  O32  1  0.798  0.195  0.628  1.0
  O  O33  1  0.298  0.805  0.372  1.0
  O  O34  1  0.213  0.805  0.865  1.0
  O  O35  1  0.713  0.195  0.135  1.0
  O  O36  1  0.918  0.012  0.893  1.0
  O  O37  1  0.418  0.988  0.107  1.0
  O  O38  1  0.084  0.999  0.604  1.0
  O  O39  1  0.584  0.001  0.396  1.0
  O  O40  1  0.894  0.637  0.842  1.0
  O  O41  1  0.394  0.363  0.158  1.0
  O  O42  1  0.105  0.360  0.643  1.0
  O  O43  1  0.605  0.640  0.357  1.0
[/CIF]
.