The crystal structure described by MgCa crystallizes in the monoclinic Cm space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Ca(1), two equivalent Ca(2), two equivalent Ca(3), one Mg(2), two equivalent Mg(1), and three equivalent Mg(3) atoms to form distorted CaCa6Mg6 cuboctahedra that share corners with six equivalent Ca(3)Ca5Mg7 cuboctahedra, corners with six equivalent Ca(1)Ca6Mg6 cuboctahedra, edges with three equivalent Ca(3)Ca5Mg7 cuboctahedra, edges with six equivalent Ca(2)Ca5Mg7 cuboctahedra, faces with two equivalent Ca(1)Ca6Mg6 cuboctahedra, faces with three equivalent Ca(2)Ca5Mg7 cuboctahedra, and faces with three equivalent Ca(3)Ca5Mg7 cuboctahedra. In the second Ca site, Ca(2) is bonded to one Ca(3), two equivalent Ca(1), two equivalent Ca(2), two equivalent Mg(2), two equivalent Mg(3), and three equivalent Mg(1) atoms to form distorted CaCa5Mg7 cuboctahedra that share corners with six equivalent Ca(2)Ca5Mg7 cuboctahedra, edges with four equivalent Ca(3)Ca5Mg7 cuboctahedra, edges with six equivalent Ca(1)Ca6Mg6 cuboctahedra, faces with two equivalent Ca(2)Ca5Mg7 cuboctahedra, faces with three equivalent Ca(1)Ca6Mg6 cuboctahedra, and faces with four equivalent Ca(3)Ca5Mg7 cuboctahedra. In the third Ca site, Ca(3) is bonded to one Ca(2), two equivalent Ca(1), two equivalent Ca(3), two equivalent Mg(1), two equivalent Mg(3), and three equivalent Mg(2) atoms to form distorted CaCa5Mg7 cuboctahedra that share corners with six equivalent Ca(3)Ca5Mg7 cuboctahedra, corners with six equivalent Ca(1)Ca6Mg6 cuboctahedra, edges with three equivalent Ca(1)Ca6Mg6 cuboctahedra, edges with four equivalent Ca(2)Ca5Mg7 cuboctahedra, faces with two equivalent Ca(3)Ca5Mg7 cuboctahedra, faces with three equivalent Ca(1)Ca6Mg6 cuboctahedra, and faces with four equivalent Ca(2)Ca5Mg7 cuboctahedra. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 9-coordinate geometry to two equivalent Ca(1), two equivalent Ca(3), three equivalent Ca(2), and two equivalent Mg(2) atoms. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one Ca(1), two equivalent Ca(2), three equivalent Ca(3), and two equivalent Mg(1) atoms. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to two equivalent Ca(2), two equivalent Ca(3), and three equivalent Ca(1) atoms. is represented by the CIF card [CIF]
data_CaMg
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.867
_cell_length_b   6.867
_cell_length_c   8.278
_cell_angle_alpha   74.771
_cell_angle_beta   74.771
_cell_angle_gamma   30.744
_symmetry_Int_Tables_number   1
_cell_volume   191.991
_cell_formula_units_Z   3
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  0.980  0.980  0.006  1.0
  Ca  Ca1  1  0.622  0.622  0.274  1.0
  Ca  Ca2  1  0.674  0.674  0.667  1.0
  Mg  Mg3  1  0.339  0.339  0.342  1.0
  Mg  Mg4  1  0.943  0.943  0.608  1.0
  Mg  Mg5  1  0.276  0.276  0.936  1.0
[/CIF]
.
The crystal structure described by MgCa crystallizes in the monoclinic Cm space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Ca(1), two equivalent Ca(2), two equivalent Ca(3), one Mg(2), two equivalent Mg(1), and three equivalent Mg(3) atoms to form distorted CaCa6Mg6 cuboctahedra that share corners with six equivalent Ca(3)Ca5Mg7 cuboctahedra, corners with six equivalent Ca(1)Ca6Mg6 cuboctahedra, edges with three equivalent Ca(3)Ca5Mg7 cuboctahedra, edges with six equivalent Ca(2)Ca5Mg7 cuboctahedra, faces with two equivalent Ca(1)Ca6Mg6 cuboctahedra, faces with three equivalent Ca(2)Ca5Mg7 cuboctahedra, and faces with three equivalent Ca(3)Ca5Mg7 cuboctahedra. In the second Ca site, Ca(2) is bonded to one Ca(3), two equivalent Ca(1), two equivalent Ca(2), two equivalent Mg(2), two equivalent Mg(3), and three equivalent Mg(1) atoms to form distorted CaCa5Mg7 cuboctahedra that share corners with six equivalent Ca(2)Ca5Mg7 cuboctahedra, edges with four equivalent Ca(3)Ca5Mg7 cuboctahedra, edges with six equivalent Ca(1)Ca6Mg6 cuboctahedra, faces with two equivalent Ca(2)Ca5Mg7 cuboctahedra, faces with three equivalent Ca(1)Ca6Mg6 cuboctahedra, and faces with four equivalent Ca(3)Ca5Mg7 cuboctahedra. In the third Ca site, Ca(3) is bonded to one Ca(2), two equivalent Ca(1), two equivalent Ca(3), two equivalent Mg(1), two equivalent Mg(3), and three equivalent Mg(2) atoms to form distorted CaCa5Mg7 cuboctahedra that share corners with six equivalent Ca(3)Ca5Mg7 cuboctahedra, corners with six equivalent Ca(1)Ca6Mg6 cuboctahedra, edges with three equivalent Ca(1)Ca6Mg6 cuboctahedra, edges with four equivalent Ca(2)Ca5Mg7 cuboctahedra, faces with two equivalent Ca(3)Ca5Mg7 cuboctahedra, faces with three equivalent Ca(1)Ca6Mg6 cuboctahedra, and faces with four equivalent Ca(2)Ca5Mg7 cuboctahedra. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 9-coordinate geometry to two equivalent Ca(1), two equivalent Ca(3), three equivalent Ca(2), and two equivalent Mg(2) atoms. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to one Ca(1), two equivalent Ca(2), three equivalent Ca(3), and two equivalent Mg(1) atoms. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to two equivalent Ca(2), two equivalent Ca(3), and three equivalent Ca(1) atoms. is represented by the CIF card [CIF]
data_CaMg
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.867
_cell_length_b   6.867
_cell_length_c   8.278
_cell_angle_alpha   74.771
_cell_angle_beta   74.771
_cell_angle_gamma   30.744
_symmetry_Int_Tables_number   1
_cell_volume   191.991
_cell_formula_units_Z   3
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  0.980  0.980  0.006  1.0
  Ca  Ca1  1  0.622  0.622  0.274  1.0
  Ca  Ca2  1  0.674  0.674  0.667  1.0
  Mg  Mg3  1  0.339  0.339  0.342  1.0
  Mg  Mg4  1  0.943  0.943  0.608  1.0
  Mg  Mg5  1  0.276  0.276  0.936  1.0
[/CIF]
.