data_Mg2AlAs
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.86
_cell_length_b   4.86
_cell_length_c   4.86
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2AlAs
_chemical_formula_sum   'Mg2 Al1 As1'
_cell_volume   81.18
_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  Mg2  1  0.0  0.0  0.0  1.0
  Mg  Mg3  1  0.15  0.15  0.15  1.0
  Al  Al0  1  0.44  0.44  0.44  1.0
  As  As1  1  0.72  0.72  0.72  1.0

data_Mg2AlAs
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.86
_cell_length_b   4.86
_cell_length_c   11.9
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Mg2AlAs
_chemical_formula_sum   'Mg6 Al3 As3'
_cell_volume   243.53
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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  3  0.0  0.0  0.0  1.0
  Mg  Mg1  3  0.0  0.0  0.85  1.0
  Al  Al2  3  0.0  0.0  0.56  1.0
  As  As3  3  0.0  0.0  0.28  1.0

Mg Mg Al As
Mg2AlAs crystallizes in the trigonal R3m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 4-coordinate geometry to one Mg(2), three equivalent Al(1), and four equivalent As(1) atoms. The Mg(1)-Mg(2) bond length is 1.85 Å. All Mg(1)-Al(1) bond lengths are 3.06 Å. There are three shorter (2.87 Å) and one longer (3.35 Å) Mg(1)-As(1) bond length. In the second Mg site, Mg(2) is bonded in a 1-coordinate geometry to one Mg(1), four equivalent Al(1), and three equivalent As(1) atoms. There are three shorter (2.87 Å) and one longer (3.35 Å) Mg(2)-Al(1) bond length. All Mg(2)-As(1) bond lengths are 3.06 Å. Al(1) is bonded in a 10-coordinate geometry to three equivalent Mg(1), four equivalent Mg(2), and three equivalent As(1) atoms. All Al(1)-As(1) bond lengths are 2.87 Å. As(1) is bonded in a 10-coordinate geometry to three equivalent Mg(2), four equivalent Mg(1), and three equivalent Al(1) atoms.