data_Ca2MgNb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.67
_cell_length_b   4.78
_cell_length_c   4.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Ca2MgNb
_chemical_formula_sum   'Ca2 Mg1 Nb1'
_cell_volume   110.53
_cell_formula_units_Z   1
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  0.34  0.0  0.47  1.0
  Ca  Ca1  1  0.0  0.39  0.47  1.0
  Mg  Mg2  1  0.0  0.0  0.0  1.0
  Nb  Nb3  1  0.34  0.39  0.0  1.0

data_Ca2MgNb
_symmetry_space_group_name_H-M   P1
_cell_length_a   4.67
_cell_length_b   4.78
_cell_length_c   4.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Ca2MgNb
_chemical_formula_sum   'Ca2 Mg1 Nb1'
_cell_volume   110.53
_cell_formula_units_Z   1
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  -0.0  0.39  0.47  1.0
  Ca  Ca1  1  0.34  0.0  0.47  1.0
  Mg  Mg2  1  0.0  0.0  0.0  1.0
  Nb  Nb3  1  0.34  0.39  -0.0  1.0

Ca Ca Mg Nb
Ca Ca Mg Nb 0 2 o o o 0 2 o o + 0 1 o o o 0 3 o o o 0 3 o o + 1 2 o o o 1 2 o o + 1 3 o o o 1 3 o o + 2 3 o o o 
Ca2MgNb crystallizes in the triclinic P1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Mg(1), and four equivalent Nb(1) atoms. The Ca(1)-Ca(2) bond length is 2.45 Å. There is one shorter (2.81 Å) and one longer (3.05 Å) Ca(1)-Mg(1) bond length. There are a spread of Ca(1)-Nb(1) bond distances ranging from 3.00-3.91 Å. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Mg(1), and four equivalent Nb(1) atoms. There is one shorter (3.00 Å) and one longer (3.21 Å) Ca(2)-Mg(1) bond length. There are a spread of Ca(2)-Nb(1) bond distances ranging from 2.81-4.05 Å. Mg(1) is bonded in a 1-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), and three equivalent Nb(1) atoms. There are a spread of Mg(1)-Nb(1) bond distances ranging from 2.45-3.63 Å. Nb(1) is bonded in a 11-coordinate geometry to four equivalent Ca(1), four equivalent Ca(2), and three equivalent Mg(1) atoms.