The structure described by Mg2Ca crystallizes in the orthorhombic Cmcm space group. Ca(1) is bonded to two equivalent Ca(1), four equivalent Mg(2), and six equivalent Mg(1) atoms to form distorted CaCa2Mg10 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with six equivalent Mg(2)Ca4Mg8 cuboctahedra, corners with six equivalent Mg(1)Ca6Mg6 cuboctahedra, edges with three equivalent Mg(2)Ca4Mg8 cuboctahedra, edges with seven equivalent Mg(1)Ca6Mg6 cuboctahedra, edges with eight equivalent Ca(1)Ca2Mg10 cuboctahedra, faces with six equivalent Ca(1)Ca2Mg10 cuboctahedra, faces with six equivalent Mg(1)Ca6Mg6 cuboctahedra, and faces with eight equivalent Mg(2)Ca4Mg8 cuboctahedra. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to six equivalent Ca(1), two equivalent Mg(2), and four equivalent Mg(1) atoms to form distorted MgCa6Mg6 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with six equivalent Mg(2)Ca4Mg8 cuboctahedra, corners with six equivalent Mg(1)Ca6Mg6 cuboctahedra, edges with seven equivalent Ca(1)Ca2Mg10 cuboctahedra, edges with eleven equivalent Mg(2)Ca4Mg8 cuboctahedra, faces with four equivalent Mg(2)Ca4Mg8 cuboctahedra, faces with six equivalent Ca(1)Ca2Mg10 cuboctahedra, and faces with ten equivalent Mg(1)Ca6Mg6 cuboctahedra. In the second Mg site, Mg(2) is bonded to four equivalent Ca(1), two equivalent Mg(1), and six equivalent Mg(2) atoms to form distorted MgCa4Mg8 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with six equivalent Mg(2)Ca4Mg8 cuboctahedra, corners with six equivalent Mg(1)Ca6Mg6 cuboctahedra, edges with three equivalent Ca(1)Ca2Mg10 cuboctahedra, edges with four equivalent Mg(2)Ca4Mg8 cuboctahedra, edges with eleven equivalent Mg(1)Ca6Mg6 cuboctahedra, faces with four equivalent Mg(1)Ca6Mg6 cuboctahedra, faces with eight equivalent Ca(1)Ca2Mg10 cuboctahedra, and faces with eight equivalent Mg(2)Ca4Mg8 cuboctahedra. is represented by the CIF card [CIF]
data_CaMg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.942
_cell_length_b   8.942
_cell_length_c   5.618
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   157.652
_symmetry_Int_Tables_number   1
_cell_volume   170.805
_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  0.108  0.892  0.250  1.0
  Ca  Ca1  1  0.892  0.108  0.750  1.0
  Mg  Mg2  1  0.442  0.558  0.250  1.0
  Mg  Mg3  1  0.780  0.220  0.250  1.0
  Mg  Mg4  1  0.220  0.780  0.750  1.0
  Mg  Mg5  1  0.558  0.442  0.750  1.0
[/CIF]
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The structure described by Mg2Ca crystallizes in the orthorhombic Cmcm space group. Ca(1) is bonded to two equivalent Ca(1), four equivalent Mg(2), and six equivalent Mg(1) atoms to form distorted CaCa2Mg10 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with six equivalent Mg(2)Ca4Mg8 cuboctahedra, corners with six equivalent Mg(1)Ca6Mg6 cuboctahedra, edges with three equivalent Mg(2)Ca4Mg8 cuboctahedra, edges with seven equivalent Mg(1)Ca6Mg6 cuboctahedra, edges with eight equivalent Ca(1)Ca2Mg10 cuboctahedra, faces with six equivalent Ca(1)Ca2Mg10 cuboctahedra, faces with six equivalent Mg(1)Ca6Mg6 cuboctahedra, and faces with eight equivalent Mg(2)Ca4Mg8 cuboctahedra. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to six equivalent Ca(1), two equivalent Mg(2), and four equivalent Mg(1) atoms to form distorted MgCa6Mg6 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with six equivalent Mg(2)Ca4Mg8 cuboctahedra, corners with six equivalent Mg(1)Ca6Mg6 cuboctahedra, edges with seven equivalent Ca(1)Ca2Mg10 cuboctahedra, edges with eleven equivalent Mg(2)Ca4Mg8 cuboctahedra, faces with four equivalent Mg(2)Ca4Mg8 cuboctahedra, faces with six equivalent Ca(1)Ca2Mg10 cuboctahedra, and faces with ten equivalent Mg(1)Ca6Mg6 cuboctahedra. In the second Mg site, Mg(2) is bonded to four equivalent Ca(1), two equivalent Mg(1), and six equivalent Mg(2) atoms to form distorted MgCa4Mg8 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with six equivalent Mg(2)Ca4Mg8 cuboctahedra, corners with six equivalent Mg(1)Ca6Mg6 cuboctahedra, edges with three equivalent Ca(1)Ca2Mg10 cuboctahedra, edges with four equivalent Mg(2)Ca4Mg8 cuboctahedra, edges with eleven equivalent Mg(1)Ca6Mg6 cuboctahedra, faces with four equivalent Mg(1)Ca6Mg6 cuboctahedra, faces with eight equivalent Ca(1)Ca2Mg10 cuboctahedra, and faces with eight equivalent Mg(2)Ca4Mg8 cuboctahedra. is represented by the CIF card [CIF]
data_CaMg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.942
_cell_length_b   8.942
_cell_length_c   5.618
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   157.652
_symmetry_Int_Tables_number   1
_cell_volume   170.805
_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  0.108  0.892  0.250  1.0
  Ca  Ca1  1  0.892  0.108  0.750  1.0
  Mg  Mg2  1  0.442  0.558  0.250  1.0
  Mg  Mg3  1  0.780  0.220  0.250  1.0
  Mg  Mg4  1  0.220  0.780  0.750  1.0
  Mg  Mg5  1  0.558  0.442  0.750  1.0
[/CIF]
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