data_MgUAs2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.87
_cell_length_b   4.87
_cell_length_c   4.87
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgUAs2
_chemical_formula_sum   'Mg1 U1 As2'
_cell_volume   81.83
_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
  U  U3  1  0.45  0.45  0.45  1.0
  As  As0  1  0.72  0.72  0.72  1.0
  As  As1  1  0.17  0.17  0.17  1.0

data_MgUAs2
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.87
_cell_length_b   4.87
_cell_length_c   11.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   MgUAs2
_chemical_formula_sum   'Mg3 U3 As6'
_cell_volume   245.49
_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
  U  U1  3  0.0  0.0  0.55  1.0
  As  As2  3  0.0  0.0  0.28  1.0
  As  As3  3  0.0  0.0  0.83  1.0

Mg U As As
MgUAs2 is Heusler structured and crystallizes in the trigonal R3m space group. Mg(1) is bonded in a distorted single-bond geometry to one As(2) and four equivalent As(1) atoms. The Mg(1)-As(2) bond length is 2.01 Å. There are three shorter (2.89 Å) and one longer (3.31 Å) Mg(1)-As(1) bond length. U(1) is bonded in a 8-coordinate geometry to four equivalent As(1) and four equivalent As(2) atoms. There are three shorter (2.89 Å) and one longer (3.31 Å) U(1)-As(1) bond length. There are three shorter (2.89 Å) and one longer (3.31 Å) U(1)-As(2) bond length. There are two inequivalent As sites. In the first As site, As(1) is bonded in a 8-coordinate geometry to four equivalent Mg(1) and four equivalent U(1) atoms. In the second As site, As(2) is bonded in a distorted single-bond geometry to one Mg(1) and four equivalent U(1) atoms.