The compound described by Mg3Nb crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Nb(1) atoms to form MgMg8Nb4 cuboctahedra that share corners with eight equivalent Nb(1)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Nb4 cuboctahedra, edges with two equivalent Mg(1)Mg8Nb4 cuboctahedra, edges with four equivalent Mg(2)Mg8Nb4 cuboctahedra, edges with four equivalent Nb(1)Mg10Nb2 cuboctahedra, edges with eight equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb4 cuboctahedra, faces with four equivalent Nb(1)Mg10Nb2 cuboctahedra, and faces with eight equivalent Mg(2)Mg8Nb4 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Nb(1) atoms to form distorted MgMg8Nb4 cuboctahedra that share corners with eight equivalent Mg(3)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(2)Mg8Nb4 cuboctahedra, edges with two equivalent Mg(2)Mg8Nb4 cuboctahedra, edges with four equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb4 cuboctahedra, edges with eight equivalent Nb(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(2)Mg8Nb4 cuboctahedra, faces with four equivalent Nb(1)Mg10Nb2 cuboctahedra, and faces with eight equivalent Mg(1)Mg8Nb4 cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with eight equivalent Mg(2)Mg8Nb4 cuboctahedra, corners with ten equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with two equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(2)Mg8Nb4 cuboctahedra, edges with four equivalent Nb(1)Mg10Nb2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb4 cuboctahedra, faces with four equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb4 cuboctahedra, faces with four equivalent Mg(2)Mg8Nb4 cuboctahedra, and faces with eight equivalent Nb(1)Mg10Nb2 cuboctahedra. Nb(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form NbMg10Nb2 cuboctahedra that share corners with eight equivalent Mg(1)Mg8Nb4 cuboctahedra, corners with ten equivalent Nb(1)Mg10Nb2 cuboctahedra, edges with two equivalent Nb(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb4 cuboctahedra, edges with eight equivalent Mg(2)Mg8Nb4 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb4 cuboctahedra, faces with four equivalent Mg(2)Mg8Nb4 cuboctahedra, faces with four equivalent Nb(1)Mg10Nb2 cuboctahedra, and faces with eight equivalent Mg(3)Mg10Nb2 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3Nb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.877
_cell_length_b   5.065
_cell_length_c   5.621
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   81.935
_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
  Mg  Mg0  1  0.000  0.000  0.653  1.0
  Mg  Mg1  1  0.000  0.500  0.327  1.0
  Mg  Mg2  1  0.500  0.500  0.864  1.0
  Nb  Nb3  1  0.500  0.000  0.155  1.0
[/CIF]
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The compound described by Mg3Nb crystallizes in the orthorhombic Pmm2 space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Nb(1) atoms to form MgMg8Nb4 cuboctahedra that share corners with eight equivalent Nb(1)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(1)Mg8Nb4 cuboctahedra, edges with two equivalent Mg(1)Mg8Nb4 cuboctahedra, edges with four equivalent Mg(2)Mg8Nb4 cuboctahedra, edges with four equivalent Nb(1)Mg10Nb2 cuboctahedra, edges with eight equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb4 cuboctahedra, faces with four equivalent Nb(1)Mg10Nb2 cuboctahedra, and faces with eight equivalent Mg(2)Mg8Nb4 cuboctahedra. In the second Mg site, Mg(2) is bonded to two equivalent Mg(1), two equivalent Mg(2), four equivalent Mg(3), and four equivalent Nb(1) atoms to form distorted MgMg8Nb4 cuboctahedra that share corners with eight equivalent Mg(3)Mg10Nb2 cuboctahedra, corners with ten equivalent Mg(2)Mg8Nb4 cuboctahedra, edges with two equivalent Mg(2)Mg8Nb4 cuboctahedra, edges with four equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb4 cuboctahedra, edges with eight equivalent Nb(1)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(2)Mg8Nb4 cuboctahedra, faces with four equivalent Nb(1)Mg10Nb2 cuboctahedra, and faces with eight equivalent Mg(1)Mg8Nb4 cuboctahedra. In the third Mg site, Mg(3) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form distorted MgMg10Nb2 cuboctahedra that share corners with eight equivalent Mg(2)Mg8Nb4 cuboctahedra, corners with ten equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with two equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(2)Mg8Nb4 cuboctahedra, edges with four equivalent Nb(1)Mg10Nb2 cuboctahedra, edges with eight equivalent Mg(1)Mg8Nb4 cuboctahedra, faces with four equivalent Mg(3)Mg10Nb2 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb4 cuboctahedra, faces with four equivalent Mg(2)Mg8Nb4 cuboctahedra, and faces with eight equivalent Nb(1)Mg10Nb2 cuboctahedra. Nb(1) is bonded to two equivalent Mg(3), four equivalent Mg(1), four equivalent Mg(2), and two equivalent Nb(1) atoms to form NbMg10Nb2 cuboctahedra that share corners with eight equivalent Mg(1)Mg8Nb4 cuboctahedra, corners with ten equivalent Nb(1)Mg10Nb2 cuboctahedra, edges with two equivalent Nb(1)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(3)Mg10Nb2 cuboctahedra, edges with four equivalent Mg(1)Mg8Nb4 cuboctahedra, edges with eight equivalent Mg(2)Mg8Nb4 cuboctahedra, faces with four equivalent Mg(1)Mg8Nb4 cuboctahedra, faces with four equivalent Mg(2)Mg8Nb4 cuboctahedra, faces with four equivalent Nb(1)Mg10Nb2 cuboctahedra, and faces with eight equivalent Mg(3)Mg10Nb2 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3Nb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.877
_cell_length_b   5.065
_cell_length_c   5.621
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   81.935
_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
  Mg  Mg0  1  0.000  0.000  0.653  1.0
  Mg  Mg1  1  0.000  0.500  0.327  1.0
  Mg  Mg2  1  0.500  0.500  0.864  1.0
  Nb  Nb3  1  0.500  0.000  0.155  1.0
[/CIF]
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