data_MgTe2As
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.18
_cell_length_b   5.18
_cell_length_c   5.18
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgTe2As
_chemical_formula_sum   'Mg1 Te2 As1'
_cell_volume   98.1
_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  Mg1  1  0.0  0.0  0.0  1.0
  Te  Te2  1  0.49  0.49  0.49  1.0
  Te  Te3  1  0.83  0.83  0.83  1.0
  As  As0  1  0.66  0.66  0.66  1.0

data_MgTe2As
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.18
_cell_length_b   5.18
_cell_length_c   12.68
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   MgTe2As
_chemical_formula_sum   'Mg3 Te6 As3'
_cell_volume   294.31
_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
  Te  Te1  3  0.0  0.0  0.17  1.0
  Te  Te2  3  0.0  0.0  0.51  1.0
  As  As3  3  0.0  0.0  0.34  1.0

Mg Te Te As
Mg Te Te As 0 2 - - - 1 3 o o o 2 3 o o o 
MgAsTe2 crystallizes in the trigonal R3m space group. Mg(1) is bonded to three equivalent As(1) and one Te(2) atom to form distorted MgTeAs3 trigonal pyramids that share  a cornercorner with one As(1)Mg3Te2 trigonal bipyramid and corners with six equivalent Mg(1)TeAs3 trigonal pyramids. All Mg(1)-As(1) bond lengths are 2.99 Å. The Mg(1)-Te(2) bond length is 2.15 Å. As(1) is bonded to three equivalent Mg(1), one Te(1), and one Te(2) atom to form AsMg3Te2 trigonal bipyramids that share corners with six equivalent As(1)Mg3Te2 trigonal bipyramids and  a cornercorner with one Mg(1)TeAs3 trigonal pyramid. The As(1)-Te(1) bond length is 2.15 Å. The As(1)-Te(2) bond length is 2.15 Å. There are two inequivalent Te sites. In the first Te site, Te(1) is bonded in a distorted single-bond geometry to one As(1) atom. In the second Te site, Te(2) is bonded in a distorted linear geometry to one Mg(1) and one As(1) atom.