The structure described by Mg6HfNb crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Hf(1), and two equivalent Nb(1) atoms to form distorted MgHf2Mg8Nb2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Nb2 cuboctahedra, corners with four equivalent Nb(1)Hf2Mg10 cuboctahedra, corners with ten equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Mg(2)Mg10Nb2 cuboctahedra, edges with two equivalent Nb(1)Hf2Mg10 cuboctahedra, edges with four equivalent Mg(4)Hf2Mg10 cuboctahedra, edges with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, and faces with eight equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Hf2Mg10 cuboctahedra, corners with six equivalent Mg(2)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Nb(1)Hf2Mg10 cuboctahedra, edges with four equivalent Mg(4)Hf2Mg10 cuboctahedra, edges with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with eight equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, and faces with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Hf(1), and two equivalent Nb(1) atoms to form distorted MgHf2Mg8Nb2 cuboctahedra that share corners with four equivalent Mg(4)Hf2Mg10 cuboctahedra, corners with ten equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Mg(4)Hf2Mg10 cuboctahedra, edges with two equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, edges with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with four equivalent Mg(2)Mg10Nb2 cuboctahedra, edges with four equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, and faces with eight equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Hf(1) atoms to form MgHf2Mg10 cuboctahedra that share corners with six equivalent Mg(4)Hf2Mg10 cuboctahedra, corners with eight equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, edges with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, edges with four equivalent Mg(2)Mg10Nb2 cuboctahedra, edges with eight equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, faces with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, and faces with six equivalent Nb(1)Hf2Mg10 cuboctahedra. Hf(1) is bonded in a 2-coordinate geometry to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms. Nb(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Hf(1) atoms to form distorted NbHf2Mg10 cuboctahedra that share corners with four equivalent Mg(2)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Hf2Mg10 cuboctahedra, corners with eight equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Mg(2)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with eight equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, faces with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, and faces with six equivalent Mg(4)Hf2Mg10 cuboctahedra. is represented by the CIF card [CIF]
data_HfMg6Nb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.963
_cell_length_b   6.181
_cell_length_c   6.427
_cell_angle_alpha   118.745
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   172.876
_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  0.500  0.696  0.392  1.0
  Mg  Mg1  1  0.000  0.819  0.148  1.0
  Mg  Mg2  1  0.000  0.329  0.148  1.0
  Mg  Mg3  1  0.000  0.329  0.658  1.0
  Mg  Mg4  1  0.500  0.684  0.852  1.0
  Mg  Mg5  1  0.500  0.168  0.852  1.0
  Mg  Mg6  1  0.500  0.171  0.341  1.0
  Nb  Nb7  1  0.000  0.804  0.608  1.0
[/CIF]
.
The structure described by Mg6HfNb crystallizes in the orthorhombic Amm2 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Hf(1), and two equivalent Nb(1) atoms to form distorted MgHf2Mg8Nb2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Nb2 cuboctahedra, corners with four equivalent Nb(1)Hf2Mg10 cuboctahedra, corners with ten equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Mg(2)Mg10Nb2 cuboctahedra, edges with two equivalent Nb(1)Hf2Mg10 cuboctahedra, edges with four equivalent Mg(4)Hf2Mg10 cuboctahedra, edges with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, and faces with eight equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Hf2Mg10 cuboctahedra, corners with six equivalent Mg(2)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Nb(1)Hf2Mg10 cuboctahedra, edges with four equivalent Mg(4)Hf2Mg10 cuboctahedra, edges with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with eight equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, and faces with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Mg(1), two equivalent Mg(2), two equivalent Mg(3), two equivalent Mg(4), two equivalent Hf(1), and two equivalent Nb(1) atoms to form distorted MgHf2Mg8Nb2 cuboctahedra that share corners with four equivalent Mg(4)Hf2Mg10 cuboctahedra, corners with ten equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Mg(4)Hf2Mg10 cuboctahedra, edges with two equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, edges with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with four equivalent Mg(2)Mg10Nb2 cuboctahedra, edges with four equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, and faces with eight equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Hf(1) atoms to form MgHf2Mg10 cuboctahedra that share corners with six equivalent Mg(4)Hf2Mg10 cuboctahedra, corners with eight equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, edges with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, edges with four equivalent Mg(2)Mg10Nb2 cuboctahedra, edges with eight equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(4)Hf2Mg10 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, faces with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, and faces with six equivalent Nb(1)Hf2Mg10 cuboctahedra. Hf(1) is bonded in a 2-coordinate geometry to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms. Nb(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Hf(1) atoms to form distorted NbHf2Mg10 cuboctahedra that share corners with four equivalent Mg(2)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Hf2Mg10 cuboctahedra, corners with eight equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with two equivalent Mg(2)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, edges with eight equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, faces with two equivalent Mg(2)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Hf2Mg10 cuboctahedra, faces with four equivalent Mg(1)Hf2Mg8Nb2 cuboctahedra, faces with four equivalent Mg(3)Hf2Mg8Nb2 cuboctahedra, and faces with six equivalent Mg(4)Hf2Mg10 cuboctahedra. is represented by the CIF card [CIF]
data_HfMg6Nb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.963
_cell_length_b   6.181
_cell_length_c   6.427
_cell_angle_alpha   118.745
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   172.876
_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  0.500  0.696  0.392  1.0
  Mg  Mg1  1  0.000  0.819  0.148  1.0
  Mg  Mg2  1  0.000  0.329  0.148  1.0
  Mg  Mg3  1  0.000  0.329  0.658  1.0
  Mg  Mg4  1  0.500  0.684  0.852  1.0
  Mg  Mg5  1  0.500  0.168  0.852  1.0
  Mg  Mg6  1  0.500  0.171  0.341  1.0
  Nb  Nb7  1  0.000  0.804  0.608  1.0
[/CIF]
.