The material structure described by Mg6NbCu 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 Nb(1), and two equivalent Cu(1) atoms to form distorted MgMg8Nb2Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Cu2 cuboctahedra, corners with four equivalent Cu(1)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Mg(2)Mg10Cu2 cuboctahedra, edges with two equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with four equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, and faces with eight equivalent Mg(3)Mg8Nb2Cu2 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 Cu(1) atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Nb2 cuboctahedra, corners with six equivalent Mg(2)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with eight equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with six equivalent Nb(1)Mg10Cu2 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 Nb(1), and two equivalent Cu(1) atoms to form distorted MgMg8Nb2Cu2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with four equivalent Nb(1)Mg10Cu2 cuboctahedra, corners with ten equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with two equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Nb(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(2)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with four equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with eight equivalent Mg(1)Mg8Nb2Cu2 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 Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Cu2 cuboctahedra, corners with six equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Nb(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(2)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with six equivalent Cu(1)Mg10Nb2 cuboctahedra. Nb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Cu(1) atoms to form NbMg10Cu2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with four equivalent Cu(1)Mg10Nb2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with six equivalent Mg(2)Mg10Cu2 cuboctahedra. Cu(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form CuMg10Nb2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Cu2 cuboctahedra, corners with six equivalent Cu(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Mg(2)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with four equivalent Nb(1)Mg10Cu2 cuboctahedra, edges with eight equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with six equivalent Mg(4)Mg10Nb2 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg6NbCu
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.837
_cell_length_b   6.053
_cell_length_c   6.194
_cell_angle_alpha   119.248
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   158.203
_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
  Cu  Cu0  1  0.000  0.816  0.633  1.0
  Mg  Mg1  1  1.000  0.827  0.171  1.0
  Mg  Mg2  1  1.000  0.344  0.171  1.0
  Mg  Mg3  1  0.000  0.331  0.661  1.0
  Mg  Mg4  1  0.500  0.676  0.837  1.0
  Mg  Mg5  1  0.500  0.161  0.837  1.0
  Mg  Mg6  1  0.500  0.167  0.334  1.0
  Nb  Nb7  1  0.500  0.678  0.356  1.0
[/CIF]
.
The material structure described by Mg6NbCu 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 Nb(1), and two equivalent Cu(1) atoms to form distorted MgMg8Nb2Cu2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Cu2 cuboctahedra, corners with four equivalent Cu(1)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Mg(2)Mg10Cu2 cuboctahedra, edges with two equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with four equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, and faces with eight equivalent Mg(3)Mg8Nb2Cu2 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 Cu(1) atoms to form distorted MgMg10Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg10Nb2 cuboctahedra, corners with six equivalent Mg(2)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Cu(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with eight equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with six equivalent Nb(1)Mg10Cu2 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 Nb(1), and two equivalent Cu(1) atoms to form distorted MgMg8Nb2Cu2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with four equivalent Nb(1)Mg10Cu2 cuboctahedra, corners with ten equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with two equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Nb(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(2)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with four equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with eight equivalent Mg(1)Mg8Nb2Cu2 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 Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with four equivalent Nb(1)Mg10Cu2 cuboctahedra, corners with six equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Nb(1)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(2)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with six equivalent Cu(1)Mg10Nb2 cuboctahedra. Nb(1) is bonded to two equivalent Mg(4), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Cu(1) atoms to form NbMg10Cu2 cuboctahedra that share corners with four equivalent Mg(4)Mg10Nb2 cuboctahedra, corners with six equivalent Nb(1)Mg10Cu2 cuboctahedra, corners with eight equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Mg(4)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, edges with four equivalent Cu(1)Mg10Nb2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with two equivalent Mg(4)Mg10Nb2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with six equivalent Mg(2)Mg10Cu2 cuboctahedra. Cu(1) is bonded to two equivalent Mg(2), four equivalent Mg(1), four equivalent Mg(3), and two equivalent Nb(1) atoms to form CuMg10Nb2 cuboctahedra that share corners with four equivalent Mg(2)Mg10Cu2 cuboctahedra, corners with six equivalent Cu(1)Mg10Nb2 cuboctahedra, corners with eight equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with two equivalent Mg(2)Mg10Cu2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, edges with four equivalent Nb(1)Mg10Cu2 cuboctahedra, edges with eight equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, faces with two equivalent Mg(2)Mg10Cu2 cuboctahedra, faces with two equivalent Nb(1)Mg10Cu2 cuboctahedra, faces with two equivalent Cu(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb2Cu2 cuboctahedra, faces with four equivalent Mg(3)Mg8Nb2Cu2 cuboctahedra, and faces with six equivalent Mg(4)Mg10Nb2 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg6NbCu
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.837
_cell_length_b   6.053
_cell_length_c   6.194
_cell_angle_alpha   119.248
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   158.203
_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
  Cu  Cu0  1  0.000  0.816  0.633  1.0
  Mg  Mg1  1  1.000  0.827  0.171  1.0
  Mg  Mg2  1  1.000  0.344  0.171  1.0
  Mg  Mg3  1  0.000  0.331  0.661  1.0
  Mg  Mg4  1  0.500  0.676  0.837  1.0
  Mg  Mg5  1  0.500  0.161  0.837  1.0
  Mg  Mg6  1  0.500  0.167  0.334  1.0
  Nb  Nb7  1  0.500  0.678  0.356  1.0
[/CIF]
.