The compound described by Mg2Sb crystallizes in the hexagonal P-6m2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to six equivalent Mg(1) and six equivalent Mg(2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(1)Mg12 cuboctahedra, corners with twelve equivalent Sb(1)Mg6 cuboctahedra, edges with six equivalent Mg(1)Mg12 cuboctahedra, edges with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, faces with two equivalent Sb(1)Mg6 cuboctahedra, faces with six equivalent Mg(1)Mg12 cuboctahedra, and faces with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra. In the second Mg site, Mg(2) is bonded to three equivalent Mg(1), six equivalent Mg(2), and three equivalent Sb(1) atoms to form distorted MgMg9Sb3 cuboctahedra that share corners with six equivalent Mg(3)Sb6 cuboctahedra, corners with six equivalent Sb(1)Mg6 cuboctahedra, corners with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Mg(1)Mg12 cuboctahedra, edges with six equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Sb(1)Mg6 cuboctahedra,  a faceface with one Mg(3)Sb6 cuboctahedra, faces with six equivalent Mg(1)Mg12 cuboctahedra, and faces with seven equivalent Mg(2)Mg9Sb3 cuboctahedra. In the third Mg site, Mg(3) is bonded to six equivalent Sb(1) atoms to form distorted MgSb6 cuboctahedra that share corners with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Mg(3)Sb6 cuboctahedra, and faces with two equivalent Mg(2)Mg9Sb3 cuboctahedra. Sb(1) is bonded to three equivalent Mg(2) and three equivalent Mg(3) atoms to form distorted SbMg6 cuboctahedra that share corners with six equivalent Mg(1)Mg12 cuboctahedra, corners with six equivalent Mg(2)Mg9Sb3 cuboctahedra, corners with six equivalent Sb(1)Mg6 cuboctahedra, edges with six equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Sb(1)Mg6 cuboctahedra,  a faceface with one Mg(1)Mg12 cuboctahedra, and  a faceface with one Sb(1)Mg6 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Sb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.313
_cell_length_b   3.313
_cell_length_c   15.561
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   147.935
_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  0.000  0.000  0.500  1.0
  Mg  Mg1  1  0.667  0.333  0.336  1.0
  Mg  Mg2  1  0.667  0.333  0.000  1.0
  Mg  Mg3  1  0.667  0.333  0.664  1.0
  Sb  Sb4  1  0.000  0.000  0.166  1.0
  Sb  Sb5  1  0.000  0.000  0.834  1.0
[/CIF]
.
The compound described by Mg2Sb crystallizes in the hexagonal P-6m2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to six equivalent Mg(1) and six equivalent Mg(2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Mg(1)Mg12 cuboctahedra, corners with twelve equivalent Sb(1)Mg6 cuboctahedra, edges with six equivalent Mg(1)Mg12 cuboctahedra, edges with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, faces with two equivalent Sb(1)Mg6 cuboctahedra, faces with six equivalent Mg(1)Mg12 cuboctahedra, and faces with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra. In the second Mg site, Mg(2) is bonded to three equivalent Mg(1), six equivalent Mg(2), and three equivalent Sb(1) atoms to form distorted MgMg9Sb3 cuboctahedra that share corners with six equivalent Mg(3)Sb6 cuboctahedra, corners with six equivalent Sb(1)Mg6 cuboctahedra, corners with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Mg(1)Mg12 cuboctahedra, edges with six equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Sb(1)Mg6 cuboctahedra,  a faceface with one Mg(3)Sb6 cuboctahedra, faces with six equivalent Mg(1)Mg12 cuboctahedra, and faces with seven equivalent Mg(2)Mg9Sb3 cuboctahedra. In the third Mg site, Mg(3) is bonded to six equivalent Sb(1) atoms to form distorted MgSb6 cuboctahedra that share corners with twelve equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Mg(3)Sb6 cuboctahedra, and faces with two equivalent Mg(2)Mg9Sb3 cuboctahedra. Sb(1) is bonded to three equivalent Mg(2) and three equivalent Mg(3) atoms to form distorted SbMg6 cuboctahedra that share corners with six equivalent Mg(1)Mg12 cuboctahedra, corners with six equivalent Mg(2)Mg9Sb3 cuboctahedra, corners with six equivalent Sb(1)Mg6 cuboctahedra, edges with six equivalent Mg(2)Mg9Sb3 cuboctahedra, edges with six equivalent Sb(1)Mg6 cuboctahedra,  a faceface with one Mg(1)Mg12 cuboctahedra, and  a faceface with one Sb(1)Mg6 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Sb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.313
_cell_length_b   3.313
_cell_length_c   15.561
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   147.935
_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  0.000  0.000  0.500  1.0
  Mg  Mg1  1  0.667  0.333  0.336  1.0
  Mg  Mg2  1  0.667  0.333  0.000  1.0
  Mg  Mg3  1  0.667  0.333  0.664  1.0
  Sb  Sb4  1  0.000  0.000  0.166  1.0
  Sb  Sb5  1  0.000  0.000  0.834  1.0
[/CIF]
.