The compound described by Cu2Mg3(PO4)3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form distorted MgO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to one O(1), one O(4), one O(5), one O(6), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Mg(2)O6 octahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a distorted square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. In the second Cu site, Cu(2) is bonded in a distorted rectangular see-saw-like geometry to four equivalent O(5) atoms. There are two inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(1) and two equivalent O(6) atoms to form PO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-59°. In the second P site, P(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-62°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mg(2), one Cu(1), and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Mg(2) and one P(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Mg(2), two equivalent Cu(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom. is represented by the CIF card [CIF]
data_Mg3Cu2(PO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.479
_cell_length_b   8.659
_cell_length_c   8.659
_cell_angle_alpha   93.876
_cell_angle_beta   108.378
_cell_angle_gamma   108.378
_symmetry_Int_Tables_number   1
_cell_volume   429.928
_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
  Mg  Mg0  1  0.750  0.230  0.770  1.0
  Mg  Mg1  1  0.250  0.770  0.230  1.0
  Mg  Mg2  1  0.630  0.558  0.873  1.0
  Mg  Mg3  1  0.370  0.442  0.127  1.0
  Mg  Mg4  1  0.870  0.127  0.442  1.0
  Mg  Mg5  1  0.130  0.873  0.558  1.0
  Cu  Cu6  1  0.000  0.000  0.000  1.0
  Cu  Cu7  1  0.500  0.000  0.000  1.0
  Cu  Cu8  1  0.750  0.503  0.497  1.0
  Cu  Cu9  1  0.250  0.497  0.503  1.0
  P  P10  1  0.750  0.800  0.200  1.0
  P  P11  1  0.250  0.200  0.800  1.0
  P  P12  1  0.873  0.382  0.163  1.0
  P  P13  1  0.127  0.618  0.837  1.0
  P  P14  1  0.627  0.837  0.618  1.0
  P  P15  1  0.373  0.163  0.382  1.0
  O  O16  1  0.774  0.781  0.025  1.0
  O  O17  1  0.226  0.219  0.975  1.0
  O  O18  1  0.726  0.975  0.219  1.0
  O  O19  1  0.274  0.025  0.781  1.0
  O  O20  1  0.684  0.457  0.112  1.0
  O  O21  1  0.316  0.543  0.888  1.0
  O  O22  1  0.816  0.888  0.543  1.0
  O  O23  1  0.184  0.112  0.457  1.0
  O  O24  1  0.799  0.219  0.036  1.0
  O  O25  1  0.201  0.781  0.964  1.0
  O  O26  1  0.701  0.964  0.781  1.0
  O  O27  1  0.299  0.036  0.219  1.0
  O  O28  1  0.892  0.493  0.832  1.0
  O  O29  1  0.108  0.507  0.168  1.0
  O  O30  1  0.608  0.168  0.507  1.0
  O  O31  1  0.392  0.832  0.493  1.0
  O  O32  1  0.576  0.652  0.651  1.0
  O  O33  1  0.424  0.348  0.349  1.0
  O  O34  1  0.924  0.349  0.348  1.0
  O  O35  1  0.076  0.651  0.652  1.0
  O  O36  1  0.530  0.685  0.222  1.0
  O  O37  1  0.470  0.315  0.778  1.0
  O  O38  1  0.970  0.778  0.315  1.0
  O  O39  1  0.030  0.222  0.685  1.0
[/CIF]
.
The compound described by Cu2Mg3(PO4)3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form distorted MgO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra, and edges with two equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to one O(1), one O(4), one O(5), one O(6), and two equivalent O(2) atoms to form MgO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent P(2)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Mg(2)O6 octahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a distorted square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. In the second Cu site, Cu(2) is bonded in a distorted rectangular see-saw-like geometry to four equivalent O(5) atoms. There are two inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(1) and two equivalent O(6) atoms to form PO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-59°. In the second P site, P(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form PO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-62°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Mg(2), one Cu(1), and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Mg(2) and one P(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(2) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Mg(2), two equivalent Cu(2), and one P(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom. is represented by the CIF card [CIF]
data_Mg3Cu2(PO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.479
_cell_length_b   8.659
_cell_length_c   8.659
_cell_angle_alpha   93.876
_cell_angle_beta   108.378
_cell_angle_gamma   108.378
_symmetry_Int_Tables_number   1
_cell_volume   429.928
_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
  Mg  Mg0  1  0.750  0.230  0.770  1.0
  Mg  Mg1  1  0.250  0.770  0.230  1.0
  Mg  Mg2  1  0.630  0.558  0.873  1.0
  Mg  Mg3  1  0.370  0.442  0.127  1.0
  Mg  Mg4  1  0.870  0.127  0.442  1.0
  Mg  Mg5  1  0.130  0.873  0.558  1.0
  Cu  Cu6  1  0.000  0.000  0.000  1.0
  Cu  Cu7  1  0.500  0.000  0.000  1.0
  Cu  Cu8  1  0.750  0.503  0.497  1.0
  Cu  Cu9  1  0.250  0.497  0.503  1.0
  P  P10  1  0.750  0.800  0.200  1.0
  P  P11  1  0.250  0.200  0.800  1.0
  P  P12  1  0.873  0.382  0.163  1.0
  P  P13  1  0.127  0.618  0.837  1.0
  P  P14  1  0.627  0.837  0.618  1.0
  P  P15  1  0.373  0.163  0.382  1.0
  O  O16  1  0.774  0.781  0.025  1.0
  O  O17  1  0.226  0.219  0.975  1.0
  O  O18  1  0.726  0.975  0.219  1.0
  O  O19  1  0.274  0.025  0.781  1.0
  O  O20  1  0.684  0.457  0.112  1.0
  O  O21  1  0.316  0.543  0.888  1.0
  O  O22  1  0.816  0.888  0.543  1.0
  O  O23  1  0.184  0.112  0.457  1.0
  O  O24  1  0.799  0.219  0.036  1.0
  O  O25  1  0.201  0.781  0.964  1.0
  O  O26  1  0.701  0.964  0.781  1.0
  O  O27  1  0.299  0.036  0.219  1.0
  O  O28  1  0.892  0.493  0.832  1.0
  O  O29  1  0.108  0.507  0.168  1.0
  O  O30  1  0.608  0.168  0.507  1.0
  O  O31  1  0.392  0.832  0.493  1.0
  O  O32  1  0.576  0.652  0.651  1.0
  O  O33  1  0.424  0.348  0.349  1.0
  O  O34  1  0.924  0.349  0.348  1.0
  O  O35  1  0.076  0.651  0.652  1.0
  O  O36  1  0.530  0.685  0.222  1.0
  O  O37  1  0.470  0.315  0.778  1.0
  O  O38  1  0.970  0.778  0.315  1.0
  O  O39  1  0.030  0.222  0.685  1.0
[/CIF]
.