data_HfMg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.99
_cell_length_b   6.99
_cell_length_c   6.99
_cell_angle_alpha   153.98
_cell_angle_beta   153.98
_cell_angle_gamma   37.13
_symmetry_Int_Tables_number   1
_chemical_formula_structural   HfMg2
_chemical_formula_sum   'Hf1 Mg2'
_cell_volume   65.51
_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
  Hf  Hf0  1  0.0  0.0  0.0  1.0
  Mg  Mg1  1  0.0  0.0  0.83  1.0
  Mg  Mg2  1  0.0  0.0  0.42  1.0

data_HfMg2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.45
_cell_length_b   4.45
_cell_length_c   6.99
_cell_angle_alpha   90.0
_cell_angle_beta   108.57
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   HfMg2
_chemical_formula_sum   'Hf2 Mg4'
_cell_volume   131.02
_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
  Hf  Hf0  2  0.0  0.0  0.0  1.0
  Mg  Mg1  2  0.0  0.0  0.17  1.0
  Mg  Mg2  2  0.0  0.0  0.58  1.0

Hf Mg Mg
Hf Mg Mg 0 1 o o - 0 2 o o o 1 2 o o o 2 2 + o + 2 2 o + + 
Mg2Hf crystallizes in the monoclinic Cm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a single-bond geometry to one Mg(2) and one Hf(1) atom. The Mg(1)-Mg(2) bond length is 2.84 Å. The Mg(1)-Hf(1) bond length is 1.22 Å. In the second Mg site, Mg(2) is bonded to one Mg(1), four equivalent Mg(2), and one Hf(1) atom to form a mixture of distorted corner and edge-sharing MgHfMg5 octahedra. The corner-sharing octahedra are not tilted. All Mg(2)-Mg(2) bond lengths are 3.15 Å. The Mg(2)-Hf(1) bond length is 2.92 Å. Hf(1) is bonded in a single-bond geometry to one Mg(1) and one Mg(2) atom.