The compound described by Ca2Mg crystallizes in the hexagonal P-6m2 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to six equivalent Ca(1) and six equivalent Ca(2) atoms to form CaCa12 cuboctahedra that share corners with six equivalent Ca(1)Ca12 cuboctahedra, corners with twelve equivalent Ca(2)Ca3Mg3 cuboctahedra, edges with six equivalent Ca(1)Ca12 cuboctahedra, edges with twelve equivalent Ca(2)Ca3Mg3 cuboctahedra, and faces with six equivalent Ca(1)Ca12 cuboctahedra. In the second Ca site, Ca(2) is bonded to three equivalent Ca(1) and three equivalent Mg(1) atoms to form distorted CaCa3Mg3 cuboctahedra that share corners with six equivalent Ca(1)Ca12 cuboctahedra, corners with six equivalent Ca(2)Ca3Mg3 cuboctahedra, corners with six equivalent Ca(3)Mg6 cuboctahedra, edges with six equivalent Ca(1)Ca12 cuboctahedra, edges with six equivalent Ca(2)Ca3Mg3 cuboctahedra,  a faceface with one Ca(2)Ca3Mg3 cuboctahedra, and  a faceface with one Ca(3)Mg6 cuboctahedra. In the third Ca site, Ca(3) is bonded to six equivalent Mg(1) atoms to form distorted CaMg6 cuboctahedra that share corners with twelve equivalent Ca(2)Ca3Mg3 cuboctahedra, edges with six equivalent Ca(3)Mg6 cuboctahedra, and faces with two equivalent Ca(2)Ca3Mg3 cuboctahedra. Mg(1) is bonded in a 6-coordinate geometry to three equivalent Ca(2) and three equivalent Ca(3) atoms. is represented by the CIF card [CIF]
data_Ca2Mg
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.786
_cell_length_b   3.786
_cell_length_c   17.502
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   217.273
_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
  Ca  Ca0  1  0.667  0.333  0.000  1.0
  Ca  Ca1  1  0.000  0.000  0.817  1.0
  Ca  Ca2  1  0.000  0.000  0.500  1.0
  Ca  Ca3  1  0.000  0.000  0.183  1.0
  Mg  Mg4  1  0.667  0.333  0.660  1.0
  Mg  Mg5  1  0.667  0.333  0.340  1.0
[/CIF]
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The compound described by Ca2Mg crystallizes in the hexagonal P-6m2 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to six equivalent Ca(1) and six equivalent Ca(2) atoms to form CaCa12 cuboctahedra that share corners with six equivalent Ca(1)Ca12 cuboctahedra, corners with twelve equivalent Ca(2)Ca3Mg3 cuboctahedra, edges with six equivalent Ca(1)Ca12 cuboctahedra, edges with twelve equivalent Ca(2)Ca3Mg3 cuboctahedra, and faces with six equivalent Ca(1)Ca12 cuboctahedra. In the second Ca site, Ca(2) is bonded to three equivalent Ca(1) and three equivalent Mg(1) atoms to form distorted CaCa3Mg3 cuboctahedra that share corners with six equivalent Ca(1)Ca12 cuboctahedra, corners with six equivalent Ca(2)Ca3Mg3 cuboctahedra, corners with six equivalent Ca(3)Mg6 cuboctahedra, edges with six equivalent Ca(1)Ca12 cuboctahedra, edges with six equivalent Ca(2)Ca3Mg3 cuboctahedra,  a faceface with one Ca(2)Ca3Mg3 cuboctahedra, and  a faceface with one Ca(3)Mg6 cuboctahedra. In the third Ca site, Ca(3) is bonded to six equivalent Mg(1) atoms to form distorted CaMg6 cuboctahedra that share corners with twelve equivalent Ca(2)Ca3Mg3 cuboctahedra, edges with six equivalent Ca(3)Mg6 cuboctahedra, and faces with two equivalent Ca(2)Ca3Mg3 cuboctahedra. Mg(1) is bonded in a 6-coordinate geometry to three equivalent Ca(2) and three equivalent Ca(3) atoms. is represented by the CIF card [CIF]
data_Ca2Mg
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.786
_cell_length_b   3.786
_cell_length_c   17.502
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   217.273
_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
  Ca  Ca0  1  0.667  0.333  0.000  1.0
  Ca  Ca1  1  0.000  0.000  0.817  1.0
  Ca  Ca2  1  0.000  0.000  0.500  1.0
  Ca  Ca3  1  0.000  0.000  0.183  1.0
  Mg  Mg4  1  0.667  0.333  0.660  1.0
  Mg  Mg5  1  0.667  0.333  0.340  1.0
[/CIF]
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