The crystal structure described by Mg3(Cu2Al)2 crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 16-coordinate geometry to one Mg(2), three equivalent Mg(1), three equivalent Cu(1), six equivalent Cu(3), and three equivalent Al(2) atoms. In the second Mg site, Mg(2) is bonded in a 16-coordinate geometry to one Mg(1), three equivalent Mg(3), two equivalent Cu(1), two equivalent Cu(2), four equivalent Cu(3), one Al(3), and three equivalent Al(1) atoms. In the third Mg site, Mg(3) is bonded in a 16-coordinate geometry to one Mg(3), three equivalent Mg(2), one Cu(1), two equivalent Cu(3), four equivalent Cu(2), two equivalent Al(3), and three equivalent Al(1) atoms. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Mg(3), two equivalent Mg(2), three equivalent Mg(1), four equivalent Cu(3), one Al(1), and one Al(2) atom to form distorted CuMg6Al2Cu4 cuboctahedra that share  a cornercorner with one Al(3)Mg6Al2Cu4 cuboctahedra, corners with two equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with two equivalent Al(2)Mg6Cu6 cuboctahedra, corners with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, corners with five equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, edges with two equivalent Al(3)Mg6Al2Cu4 cuboctahedra, edges with four equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, faces with two equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, faces with three equivalent Al(1)Mg6AlCu5 cuboctahedra, faces with three equivalent Al(2)Mg6Cu6 cuboctahedra, and faces with ten equivalent Cu(3)Mg6Al2Cu4 cuboctahedra. In the second Cu site, Cu(2) is bonded to two equivalent Mg(2), four equivalent Mg(3), two equivalent Cu(2), two equivalent Al(1), and two equivalent Al(3) atoms to form CuMg6Al4Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, corners with four equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with six equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, edges with two equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, edges with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, faces with two equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, faces with two equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, faces with four equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, faces with four equivalent Al(3)Mg6Al2Cu4 cuboctahedra, and faces with six equivalent Al(1)Mg6AlCu5 cuboctahedra. In the third Cu site, Cu(3) is bonded to one Mg(3), two equivalent Mg(2), three equivalent Mg(1), two equivalent Cu(1), two equivalent Cu(3), one Al(1), and one Al(2) atom to form distorted CuMg6Al2Cu4 cuboctahedra that share corners with two equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with two equivalent Al(3)Mg6Al2Cu4 cuboctahedra, corners with two equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with two equivalent Al(2)Mg6Cu6 cuboctahedra, corners with three equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, corners with seven equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, edges with two equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, edges with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra,  a faceface with one Cu(2)Mg6Al4Cu2 cuboctahedra,  a faceface with one Al(3)Mg6Al2Cu4 cuboctahedra, faces with three equivalent Al(1)Mg6AlCu5 cuboctahedra, faces with three equivalent Al(2)Mg6Cu6 cuboctahedra, faces with five equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, and faces with five equivalent Cu(3)Mg6Al2Cu4 cuboctahedra. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent Mg(2), three equivalent Mg(3), one Cu(1), two equivalent Cu(2), two equivalent Cu(3), and one Al(3) atom to form distorted AlMg6AlCu5 cuboctahedra that share corners with two equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with two equivalent Al(3)Mg6Al2Cu4 cuboctahedra, corners with three equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with three equivalent Al(2)Mg6Cu6 cuboctahedra, corners with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, edges with six equivalent Al(1)Mg6AlCu5 cuboctahedra, faces with three equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, faces with three equivalent Al(3)Mg6Al2Cu4 cuboctahedra, faces with six equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, and faces with six equivalent Cu(2)Mg6Al4Cu2 cuboctahedra. In the second Al site, Al(2) is bonded to six equivalent Mg(1), two equivalent Cu(1), and four equivalent Cu(3) atoms to form distorted AlMg6Cu6 cuboctahedra that share corners with four equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with six equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with eight equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, edges with six equivalent Al(2)Mg6Cu6 cuboctahedra, faces with six equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, and faces with twelve equivalent Cu(3)Mg6Al2Cu4 cuboctahedra. In the third Al site, Al(3) is bonded to two equivalent Mg(2), four equivalent Mg(3), four equivalent Cu(2), and two equivalent Al(1) atoms to form distorted AlMg6Al2Cu4 cuboctahedra that share corners with two equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Al(3)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with eight equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, edges with two equivalent Al(3)Mg6Al2Cu4 cuboctahedra, edges with four equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, faces with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, faces with six equivalent Al(1)Mg6AlCu5 cuboctahedra, and faces with eight equivalent Cu(2)Mg6Al4Cu2 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3(AlCu2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.044
_cell_length_b   5.044
_cell_length_c   12.149
_cell_angle_alpha   89.402
_cell_angle_beta   89.402
_cell_angle_gamma   60.306
_symmetry_Int_Tables_number   1
_cell_volume   268.492
_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  0.166  0.166  0.539  1.0
  Mg  Mg1  1  0.837  0.837  0.218  1.0
  Mg  Mg2  1  0.493  0.493  0.871  1.0
  Mg  Mg3  1  0.834  0.834  0.461  1.0
  Mg  Mg4  1  0.507  0.507  0.129  1.0
  Mg  Mg5  1  0.163  0.163  0.782  1.0
  Al  Al6  1  0.177  0.177  0.172  1.0
  Al  Al7  1  0.823  0.823  0.828  1.0
  Al  Al8  1  0.500  0.500  0.500  1.0
  Al  Al9  1  0.000  0.000  0.000  1.0
  Cu  Cu10  1  0.666  0.666  0.663  1.0
  Cu  Cu11  1  0.334  0.334  0.337  1.0
  Cu  Cu12  1  0.000  0.500  0.000  1.0
  Cu  Cu13  1  0.666  0.166  0.666  1.0
  Cu  Cu14  1  0.334  0.834  0.334  1.0
  Cu  Cu15  1  0.834  0.334  0.334  1.0
  Cu  Cu16  1  0.500  0.000  0.000  1.0
  Cu  Cu17  1  0.166  0.666  0.666  1.0
[/CIF]
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The crystal structure described by Mg3(Cu2Al)2 crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 16-coordinate geometry to one Mg(2), three equivalent Mg(1), three equivalent Cu(1), six equivalent Cu(3), and three equivalent Al(2) atoms. In the second Mg site, Mg(2) is bonded in a 16-coordinate geometry to one Mg(1), three equivalent Mg(3), two equivalent Cu(1), two equivalent Cu(2), four equivalent Cu(3), one Al(3), and three equivalent Al(1) atoms. In the third Mg site, Mg(3) is bonded in a 16-coordinate geometry to one Mg(3), three equivalent Mg(2), one Cu(1), two equivalent Cu(3), four equivalent Cu(2), two equivalent Al(3), and three equivalent Al(1) atoms. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Mg(3), two equivalent Mg(2), three equivalent Mg(1), four equivalent Cu(3), one Al(1), and one Al(2) atom to form distorted CuMg6Al2Cu4 cuboctahedra that share  a cornercorner with one Al(3)Mg6Al2Cu4 cuboctahedra, corners with two equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with two equivalent Al(2)Mg6Cu6 cuboctahedra, corners with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, corners with five equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, edges with two equivalent Al(3)Mg6Al2Cu4 cuboctahedra, edges with four equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, faces with two equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, faces with three equivalent Al(1)Mg6AlCu5 cuboctahedra, faces with three equivalent Al(2)Mg6Cu6 cuboctahedra, and faces with ten equivalent Cu(3)Mg6Al2Cu4 cuboctahedra. In the second Cu site, Cu(2) is bonded to two equivalent Mg(2), four equivalent Mg(3), two equivalent Cu(2), two equivalent Al(1), and two equivalent Al(3) atoms to form CuMg6Al4Cu2 cuboctahedra that share corners with four equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, corners with four equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with six equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, edges with two equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, edges with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, faces with two equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, faces with two equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, faces with four equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, faces with four equivalent Al(3)Mg6Al2Cu4 cuboctahedra, and faces with six equivalent Al(1)Mg6AlCu5 cuboctahedra. In the third Cu site, Cu(3) is bonded to one Mg(3), two equivalent Mg(2), three equivalent Mg(1), two equivalent Cu(1), two equivalent Cu(3), one Al(1), and one Al(2) atom to form distorted CuMg6Al2Cu4 cuboctahedra that share corners with two equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with two equivalent Al(3)Mg6Al2Cu4 cuboctahedra, corners with two equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with two equivalent Al(2)Mg6Cu6 cuboctahedra, corners with three equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, corners with seven equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, edges with two equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, edges with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra,  a faceface with one Cu(2)Mg6Al4Cu2 cuboctahedra,  a faceface with one Al(3)Mg6Al2Cu4 cuboctahedra, faces with three equivalent Al(1)Mg6AlCu5 cuboctahedra, faces with three equivalent Al(2)Mg6Cu6 cuboctahedra, faces with five equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, and faces with five equivalent Cu(3)Mg6Al2Cu4 cuboctahedra. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to three equivalent Mg(2), three equivalent Mg(3), one Cu(1), two equivalent Cu(2), two equivalent Cu(3), and one Al(3) atom to form distorted AlMg6AlCu5 cuboctahedra that share corners with two equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with two equivalent Al(3)Mg6Al2Cu4 cuboctahedra, corners with three equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with three equivalent Al(2)Mg6Cu6 cuboctahedra, corners with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Cu(2)Mg6Al4Cu2 cuboctahedra, edges with six equivalent Al(1)Mg6AlCu5 cuboctahedra, faces with three equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, faces with three equivalent Al(3)Mg6Al2Cu4 cuboctahedra, faces with six equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, and faces with six equivalent Cu(2)Mg6Al4Cu2 cuboctahedra. In the second Al site, Al(2) is bonded to six equivalent Mg(1), two equivalent Cu(1), and four equivalent Cu(3) atoms to form distorted AlMg6Cu6 cuboctahedra that share corners with four equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with six equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with eight equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, edges with six equivalent Al(2)Mg6Cu6 cuboctahedra, faces with six equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, and faces with twelve equivalent Cu(3)Mg6Al2Cu4 cuboctahedra. In the third Al site, Al(3) is bonded to two equivalent Mg(2), four equivalent Mg(3), four equivalent Cu(2), and two equivalent Al(1) atoms to form distorted AlMg6Al2Cu4 cuboctahedra that share corners with two equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Al(3)Mg6Al2Cu4 cuboctahedra, corners with four equivalent Al(1)Mg6AlCu5 cuboctahedra, corners with eight equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, edges with two equivalent Al(3)Mg6Al2Cu4 cuboctahedra, edges with four equivalent Cu(1)Mg6Al2Cu4 cuboctahedra, faces with four equivalent Cu(3)Mg6Al2Cu4 cuboctahedra, faces with six equivalent Al(1)Mg6AlCu5 cuboctahedra, and faces with eight equivalent Cu(2)Mg6Al4Cu2 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3(AlCu2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.044
_cell_length_b   5.044
_cell_length_c   12.149
_cell_angle_alpha   89.402
_cell_angle_beta   89.402
_cell_angle_gamma   60.306
_symmetry_Int_Tables_number   1
_cell_volume   268.492
_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  0.166  0.166  0.539  1.0
  Mg  Mg1  1  0.837  0.837  0.218  1.0
  Mg  Mg2  1  0.493  0.493  0.871  1.0
  Mg  Mg3  1  0.834  0.834  0.461  1.0
  Mg  Mg4  1  0.507  0.507  0.129  1.0
  Mg  Mg5  1  0.163  0.163  0.782  1.0
  Al  Al6  1  0.177  0.177  0.172  1.0
  Al  Al7  1  0.823  0.823  0.828  1.0
  Al  Al8  1  0.500  0.500  0.500  1.0
  Al  Al9  1  0.000  0.000  0.000  1.0
  Cu  Cu10  1  0.666  0.666  0.663  1.0
  Cu  Cu11  1  0.334  0.334  0.337  1.0
  Cu  Cu12  1  0.000  0.500  0.000  1.0
  Cu  Cu13  1  0.666  0.166  0.666  1.0
  Cu  Cu14  1  0.334  0.834  0.334  1.0
  Cu  Cu15  1  0.834  0.334  0.334  1.0
  Cu  Cu16  1  0.500  0.000  0.000  1.0
  Cu  Cu17  1  0.166  0.666  0.666  1.0
[/CIF]
.