data_PuMg3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.08
_cell_length_b   5.08
_cell_length_c   5.08
_cell_angle_alpha   117.55
_cell_angle_beta   117.55
_cell_angle_gamma   94.3
_symmetry_Int_Tables_number   1
_chemical_formula_structural   PuMg3
_chemical_formula_sum   'Pu1 Mg3'
_cell_volume   95.57
_cell_formula_units_Z   1
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
  Pu  Pu3  1  0.0  0.0  0.45  1.0
  Mg  Mg0  1  0.0  0.0  0.0  1.0
  Mg  Mg1  1  0.63  0.0  0.73  1.0
  Mg  Mg2  1  0.0  0.63  0.73  1.0

data_PuMg3
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.9
_cell_length_b   7.44
_cell_length_c   5.08
_cell_angle_alpha   90.0
_cell_angle_beta   132.85
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   PuMg3
_chemical_formula_sum   'Pu2 Mg6'
_cell_volume   191.13
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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
  Pu  Pu0  2  0.05  0.5  0.55  1.0
  Mg  Mg1  4  0.09  0.18  0.27  1.0
  Mg  Mg2  2  0.0  0.0  0.0  1.0

Pu Mg Mg Mg
Pu Mg Mg Mg 0 3 o o o 0 3 o - o 0 2 - o o 0 2 o o o 0 1 o o o 0 1 o o + 1 2 - o - 1 3 o - - 
Mg3Pu crystallizes in the monoclinic Cm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(2) and two equivalent Pu(1) atoms. Both Mg(1)-Mg(2) bond lengths are 1.74 Å. There is one shorter (2.29 Å) and one longer (2.78 Å) Mg(1)-Pu(1) bond length. In the second Mg site, Mg(2) is bonded in a 1-coordinate geometry to one Mg(1) and two equivalent Pu(1) atoms. There is one shorter (2.80 Å) and one longer (2.84 Å) Mg(2)-Pu(1) bond length. Pu(1) is bonded in a 6-coordinate geometry to two equivalent Mg(1) and four equivalent Mg(2) atoms.