The compound described by Mg2Ca is beta-derived structured and crystallizes in the trigonal P-3m1 space group. Ca(1) is bonded to nine equivalent Ca(1) and three equivalent Mg(1) atoms to form distorted CaCa9Mg3 cuboctahedra that share corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra, corners with six equivalent Mg(1)Ca3Mg9 cuboctahedra, corners with six equivalent Mg(2)Mg12 cuboctahedra, edges with six equivalent Mg(1)Ca3Mg9 cuboctahedra, edges with twelve equivalent Ca(1)Ca9Mg3 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra, faces with seven equivalent Mg(1)Ca3Mg9 cuboctahedra, and faces with twelve equivalent Ca(1)Ca9Mg3 cuboctahedra. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent Ca(1), three equivalent Mg(2), and six equivalent Mg(1) atoms to form distorted MgCa3Mg9 cuboctahedra that share corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra; corners with six equivalent Mg(1)Ca3Mg9 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; edges with six equivalent Ca(1)Ca9Mg3 cuboctahedra; edges with six equivalent Mg(1)Ca3Mg9 cuboctahedra; edges with six equivalent Mg(2)Mg12 cuboctahedra; faces with six equivalent Mg(1)Ca3Mg9 cuboctahedra; faces with seven equivalent Ca(1)Ca9Mg3 cuboctahedra; and faces with seven Mg(2,2)Mg12 cuboctahedra. In the second Mg site, Mg(2) is bonded to three equivalent Mg(1) and nine Mg(2,2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra; corners with six equivalent Mg(1)Ca3Mg9 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; edges with six equivalent Mg(1)Ca3Mg9 cuboctahedra; edges with twelve Mg(2,2)Mg12 cuboctahedra;  a faceface with one Ca(1)Ca9Mg3 cuboctahedra; faces with seven equivalent Mg(1)Ca3Mg9 cuboctahedra; and faces with twelve Mg(2,2)Mg12 cuboctahedra. In the third Mg site, Mg(2) is bonded to three equivalent Mg(1) and nine Mg(2,2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra; corners with six equivalent Mg(1)Ca3Mg9 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; edges with six equivalent Mg(1)Ca3Mg9 cuboctahedra; edges with twelve Mg(2,2)Mg12 cuboctahedra;  a faceface with one Ca(1)Ca9Mg3 cuboctahedra; faces with seven equivalent Mg(1)Ca3Mg9 cuboctahedra; and faces with twelve Mg(2,2)Mg12 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaMg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.445
_cell_length_b   3.445
_cell_length_c   16.887
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   173.575
_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  0.096  1.0
  Ca  Ca1  1  0.333  0.667  0.904  1.0
  Mg  Mg2  1  0.333  0.667  0.266  1.0
  Mg  Mg3  1  0.667  0.333  0.422  1.0
  Mg  Mg4  1  0.333  0.667  0.578  1.0
  Mg  Mg5  1  0.667  0.333  0.734  1.0
[/CIF]
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The compound described by Mg2Ca is beta-derived structured and crystallizes in the trigonal P-3m1 space group. Ca(1) is bonded to nine equivalent Ca(1) and three equivalent Mg(1) atoms to form distorted CaCa9Mg3 cuboctahedra that share corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra, corners with six equivalent Mg(1)Ca3Mg9 cuboctahedra, corners with six equivalent Mg(2)Mg12 cuboctahedra, edges with six equivalent Mg(1)Ca3Mg9 cuboctahedra, edges with twelve equivalent Ca(1)Ca9Mg3 cuboctahedra,  a faceface with one Mg(2)Mg12 cuboctahedra, faces with seven equivalent Mg(1)Ca3Mg9 cuboctahedra, and faces with twelve equivalent Ca(1)Ca9Mg3 cuboctahedra. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent Ca(1), three equivalent Mg(2), and six equivalent Mg(1) atoms to form distorted MgCa3Mg9 cuboctahedra that share corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra; corners with six equivalent Mg(1)Ca3Mg9 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; edges with six equivalent Ca(1)Ca9Mg3 cuboctahedra; edges with six equivalent Mg(1)Ca3Mg9 cuboctahedra; edges with six equivalent Mg(2)Mg12 cuboctahedra; faces with six equivalent Mg(1)Ca3Mg9 cuboctahedra; faces with seven equivalent Ca(1)Ca9Mg3 cuboctahedra; and faces with seven Mg(2,2)Mg12 cuboctahedra. In the second Mg site, Mg(2) is bonded to three equivalent Mg(1) and nine Mg(2,2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra; corners with six equivalent Mg(1)Ca3Mg9 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; edges with six equivalent Mg(1)Ca3Mg9 cuboctahedra; edges with twelve Mg(2,2)Mg12 cuboctahedra;  a faceface with one Ca(1)Ca9Mg3 cuboctahedra; faces with seven equivalent Mg(1)Ca3Mg9 cuboctahedra; and faces with twelve Mg(2,2)Mg12 cuboctahedra. In the third Mg site, Mg(2) is bonded to three equivalent Mg(1) and nine Mg(2,2) atoms to form MgMg12 cuboctahedra that share corners with six equivalent Ca(1)Ca9Mg3 cuboctahedra; corners with six equivalent Mg(1)Ca3Mg9 cuboctahedra; corners with six equivalent Mg(2)Mg12 cuboctahedra; edges with six equivalent Mg(1)Ca3Mg9 cuboctahedra; edges with twelve Mg(2,2)Mg12 cuboctahedra;  a faceface with one Ca(1)Ca9Mg3 cuboctahedra; faces with seven equivalent Mg(1)Ca3Mg9 cuboctahedra; and faces with twelve Mg(2,2)Mg12 cuboctahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaMg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.445
_cell_length_b   3.445
_cell_length_c   16.887
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   173.575
_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  0.096  1.0
  Ca  Ca1  1  0.333  0.667  0.904  1.0
  Mg  Mg2  1  0.333  0.667  0.266  1.0
  Mg  Mg3  1  0.667  0.333  0.422  1.0
  Mg  Mg4  1  0.333  0.667  0.578  1.0
  Mg  Mg5  1  0.667  0.333  0.734  1.0
[/CIF]
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