data_CaMg2As
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.16
_cell_length_b   5.16
_cell_length_c   5.16
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CaMg2As
_chemical_formula_sum   'Ca1 Mg2 As1'
_cell_volume   97.14
_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
  Ca  Ca1  1  0.0  0.0  0.0  1.0
  Mg  Mg2  1  0.82  0.82  0.82  1.0
  Mg  Mg3  1  0.47  0.47  0.47  1.0
  As  As0  1  0.65  0.65  0.65  1.0

data_CaMg2As
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.16
_cell_length_b   5.16
_cell_length_c   12.64
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   CaMg2As
_chemical_formula_sum   'Ca3 Mg6 As3'
_cell_volume   291.41
_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
  Ca  Ca0  3  0.0  0.0  0.0  1.0
  Mg  Mg1  3  0.0  0.0  0.18  1.0
  Mg  Mg2  3  0.0  0.0  0.53  1.0
  As  As3  3  0.0  0.0  0.35  1.0

Ca Mg Mg As
CaMg2As crystallizes in the trigonal R3m space group. Ca(1) is bonded to one Mg(1) and three equivalent As(1) atoms to form distorted CaMgAs3 trigonal pyramids that share  a cornercorner with one As(1)Ca3Mg2 trigonal bipyramid and corners with six equivalent Ca(1)MgAs3 trigonal pyramids. The Ca(1)-Mg(1) bond length is 2.22 Å. All Ca(1)-As(1) bond lengths are 2.99 Å. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted linear geometry to one Ca(1) and one As(1) atom. The Mg(1)-As(1) bond length is 2.22 Å. In the second Mg site, Mg(2) is bonded in a single-bond geometry to one As(1) atom. The Mg(2)-As(1) bond length is 2.22 Å. As(1) is bonded to three equivalent Ca(1), one Mg(1), and one Mg(2) atom to form distorted AsCa3Mg2 trigonal bipyramids that share corners with six equivalent As(1)Ca3Mg2 trigonal bipyramids and  a cornercorner with one Ca(1)MgAs3 trigonal pyramid.