The compound described by BaCa2MgSi2O8 crystallizes in the trigonal P-3 space group. Ba(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share edges with six equivalent Ba(1)O12 cuboctahedra, edges with six equivalent Si(1)O4 tetrahedra, and faces with two equivalent Mg(1)O6 octahedra. Ca(1) is bonded in a 4-coordinate geometry to one O(1) and three equivalent O(2) atoms. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and faces with two equivalent Ba(1)O12 cuboctahedra. Si(1) is bonded to one O(1) and three equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 24°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to three equivalent Ba(1), one Ca(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ba(1), one Ca(1), one Mg(1), and one Si(1) atom. is represented by the CIF file [CIF]
data_BaCa2Mg(SiO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.485
_cell_length_b   5.485
_cell_length_c   6.897
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   179.683
_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
  Ba  Ba0  1  0.000  0.000  0.500  1.0
  Ca  Ca1  1  0.333  0.667  0.838  1.0
  Ca  Ca2  1  0.667  0.333  0.162  1.0
  Mg  Mg3  1  0.000  0.000  0.000  1.0
  Si  Si4  1  0.333  0.667  0.272  1.0
  Si  Si5  1  0.667  0.333  0.728  1.0
  O  O6  1  0.333  0.667  0.508  1.0
  O  O7  1  0.667  0.333  0.492  1.0
  O  O8  1  0.646  0.883  0.176  1.0
  O  O9  1  0.117  0.763  0.176  1.0
  O  O10  1  0.237  0.354  0.176  1.0
  O  O11  1  0.354  0.117  0.824  1.0
  O  O12  1  0.883  0.237  0.824  1.0
  O  O13  1  0.763  0.646  0.824  1.0
[/CIF]
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The compound described by BaCa2MgSi2O8 crystallizes in the trigonal P-3 space group. Ba(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share edges with six equivalent Ba(1)O12 cuboctahedra, edges with six equivalent Si(1)O4 tetrahedra, and faces with two equivalent Mg(1)O6 octahedra. Ca(1) is bonded in a 4-coordinate geometry to one O(1) and three equivalent O(2) atoms. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and faces with two equivalent Ba(1)O12 cuboctahedra. Si(1) is bonded to one O(1) and three equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 24°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to three equivalent Ba(1), one Ca(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ba(1), one Ca(1), one Mg(1), and one Si(1) atom. is represented by the CIF file [CIF]
data_BaCa2Mg(SiO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.485
_cell_length_b   5.485
_cell_length_c   6.897
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   179.683
_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
  Ba  Ba0  1  0.000  0.000  0.500  1.0
  Ca  Ca1  1  0.333  0.667  0.838  1.0
  Ca  Ca2  1  0.667  0.333  0.162  1.0
  Mg  Mg3  1  0.000  0.000  0.000  1.0
  Si  Si4  1  0.333  0.667  0.272  1.0
  Si  Si5  1  0.667  0.333  0.728  1.0
  O  O6  1  0.333  0.667  0.508  1.0
  O  O7  1  0.667  0.333  0.492  1.0
  O  O8  1  0.646  0.883  0.176  1.0
  O  O9  1  0.117  0.763  0.176  1.0
  O  O10  1  0.237  0.354  0.176  1.0
  O  O11  1  0.354  0.117  0.824  1.0
  O  O12  1  0.883  0.237  0.824  1.0
  O  O13  1  0.763  0.646  0.824  1.0
[/CIF]
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