The structure described by Mg3(PO4)2 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-63°. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with four equivalent Mg(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 57-63°. 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 Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-57°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one P(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3(PO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.726
_cell_length_b   5.890
_cell_length_c   10.195
_cell_angle_alpha   89.197
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   283.739
_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  0.513  0.762  0.778  1.0
  Mg  Mg1  1  0.013  0.238  0.722  1.0
  Mg  Mg2  1  0.987  0.762  0.278  1.0
  Mg  Mg3  1  0.000  0.500  0.000  1.0
  Mg  Mg4  1  0.487  0.238  0.222  1.0
  Mg  Mg5  1  0.500  0.500  0.500  1.0
  P  P6  1  0.925  0.256  0.403  1.0
  P  P7  1  0.425  0.744  0.097  1.0
  P  P8  1  0.075  0.744  0.597  1.0
  P  P9  1  0.575  0.256  0.903  1.0
  O  O10  1  0.746  0.725  0.104  1.0
  O  O11  1  0.687  0.255  0.044  1.0
  O  O12  1  0.254  0.275  0.896  1.0
  O  O13  1  0.230  0.532  0.661  1.0
  O  O14  1  0.809  0.059  0.323  1.0
  O  O15  1  0.691  0.059  0.823  1.0
  O  O16  1  0.309  0.941  0.177  1.0
  O  O17  1  0.313  0.745  0.956  1.0
  O  O18  1  0.187  0.745  0.456  1.0
  O  O19  1  0.191  0.941  0.677  1.0
  O  O20  1  0.270  0.532  0.161  1.0
  O  O21  1  0.246  0.275  0.396  1.0
  O  O22  1  0.730  0.468  0.839  1.0
  O  O23  1  0.770  0.468  0.339  1.0
  O  O24  1  0.754  0.725  0.604  1.0
  O  O25  1  0.813  0.255  0.544  1.0
[/CIF]
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The structure described by Mg3(PO4)2 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra, and  an edgeedge with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-63°. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with four equivalent Mg(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 57-63°. 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 Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-57°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one P(1) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one P(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3(PO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.726
_cell_length_b   5.890
_cell_length_c   10.195
_cell_angle_alpha   89.197
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   283.739
_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  0.513  0.762  0.778  1.0
  Mg  Mg1  1  0.013  0.238  0.722  1.0
  Mg  Mg2  1  0.987  0.762  0.278  1.0
  Mg  Mg3  1  0.000  0.500  0.000  1.0
  Mg  Mg4  1  0.487  0.238  0.222  1.0
  Mg  Mg5  1  0.500  0.500  0.500  1.0
  P  P6  1  0.925  0.256  0.403  1.0
  P  P7  1  0.425  0.744  0.097  1.0
  P  P8  1  0.075  0.744  0.597  1.0
  P  P9  1  0.575  0.256  0.903  1.0
  O  O10  1  0.746  0.725  0.104  1.0
  O  O11  1  0.687  0.255  0.044  1.0
  O  O12  1  0.254  0.275  0.896  1.0
  O  O13  1  0.230  0.532  0.661  1.0
  O  O14  1  0.809  0.059  0.323  1.0
  O  O15  1  0.691  0.059  0.823  1.0
  O  O16  1  0.309  0.941  0.177  1.0
  O  O17  1  0.313  0.745  0.956  1.0
  O  O18  1  0.187  0.745  0.456  1.0
  O  O19  1  0.191  0.941  0.677  1.0
  O  O20  1  0.270  0.532  0.161  1.0
  O  O21  1  0.246  0.275  0.396  1.0
  O  O22  1  0.730  0.468  0.839  1.0
  O  O23  1  0.770  0.468  0.339  1.0
  O  O24  1  0.754  0.725  0.604  1.0
  O  O25  1  0.813  0.255  0.544  1.0
[/CIF]
.