The structure described by Mg2Ca crystallizes in the monoclinic Cm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Ca(1), two equivalent Ca(2), one Mg(3), two equivalent Mg(1), two equivalent Mg(4), and three equivalent Mg(2) atoms to form a mixture of distorted face and corner-sharing CaCa4Mg8 cuboctahedra. In the second Ca site, Ca(2) is bonded in a 12-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Mg(1), two equivalent Mg(2), two equivalent Mg(4), and three equivalent Mg(3) atoms. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 3-coordinate geometry to one Ca(2), two equivalent Ca(1), two equivalent Mg(2), two equivalent Mg(3), and two equivalent Mg(4) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Ca(2), three equivalent Ca(1), one Mg(4), two equivalent Mg(1), and two equivalent Mg(2) atoms. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to one Ca(1), three equivalent Ca(2), two equivalent Mg(1), two equivalent Mg(3), and two equivalent Mg(4) atoms. In the fourth Mg site, Mg(4) is bonded in a 11-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Mg(2), two equivalent Mg(1), two equivalent Mg(3), and two equivalent Mg(4) atoms. is represented by the CIF file [CIF]
data_CaMg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.759
_cell_length_b   6.759
_cell_length_c   7.929
_cell_angle_alpha   78.225
_cell_angle_beta   78.225
_cell_angle_gamma   29.569
_symmetry_Int_Tables_number   1
_cell_volume   174.724
_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  0.619  0.619  0.263  1.0
  Ca  Ca1  1  0.938  0.938  0.621  1.0
  Mg  Mg2  1  0.994  0.994  0.002  1.0
  Mg  Mg3  1  0.336  0.336  0.321  1.0
  Mg  Mg4  1  0.669  0.669  0.678  1.0
  Mg  Mg5  1  0.277  0.277  0.947  1.0
[/CIF]
.
The structure described by Mg2Ca crystallizes in the monoclinic Cm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Ca(1), two equivalent Ca(2), one Mg(3), two equivalent Mg(1), two equivalent Mg(4), and three equivalent Mg(2) atoms to form a mixture of distorted face and corner-sharing CaCa4Mg8 cuboctahedra. In the second Ca site, Ca(2) is bonded in a 12-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Mg(1), two equivalent Mg(2), two equivalent Mg(4), and three equivalent Mg(3) atoms. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 3-coordinate geometry to one Ca(2), two equivalent Ca(1), two equivalent Mg(2), two equivalent Mg(3), and two equivalent Mg(4) atoms. In the second Mg site, Mg(2) is bonded in a 10-coordinate geometry to two equivalent Ca(2), three equivalent Ca(1), one Mg(4), two equivalent Mg(1), and two equivalent Mg(2) atoms. In the third Mg site, Mg(3) is bonded in a 10-coordinate geometry to one Ca(1), three equivalent Ca(2), two equivalent Mg(1), two equivalent Mg(3), and two equivalent Mg(4) atoms. In the fourth Mg site, Mg(4) is bonded in a 11-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Mg(2), two equivalent Mg(1), two equivalent Mg(3), and two equivalent Mg(4) atoms. is represented by the CIF file [CIF]
data_CaMg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.759
_cell_length_b   6.759
_cell_length_c   7.929
_cell_angle_alpha   78.225
_cell_angle_beta   78.225
_cell_angle_gamma   29.569
_symmetry_Int_Tables_number   1
_cell_volume   174.724
_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  0.619  0.619  0.263  1.0
  Ca  Ca1  1  0.938  0.938  0.621  1.0
  Mg  Mg2  1  0.994  0.994  0.002  1.0
  Mg  Mg3  1  0.336  0.336  0.321  1.0
  Mg  Mg4  1  0.669  0.669  0.678  1.0
  Mg  Mg5  1  0.277  0.277  0.947  1.0
[/CIF]
.