The compound described by Na2Ca2Si3O9 crystallizes in the trigonal R3m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(5) atoms. In the second Na site, Na(2) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form distorted NaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and  a faceface with one Ca(2)O6 octahedra. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form CaO6 octahedra that share corners with three equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and  a faceface with one Na(2)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), and two equivalent O(5) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ca(2)O6 octahedra, corners with two equivalent Na(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 39-48°. In the second Si site, Si(2) is bonded to one O(2), one O(4), and two equivalent O(5) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ca(2)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Ca(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Ca(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(2), one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to two equivalent Na(1), one Ca(1), one Si(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Ca2(SiO3)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.595
_cell_length_b   7.595
_cell_length_c   7.595
_cell_angle_alpha   88.790
_cell_angle_beta   88.790
_cell_angle_gamma   88.790
_symmetry_Int_Tables_number   1
_cell_volume   437.778
_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
  Na  Na0  1  0.485  0.485  0.019  1.0
  Na  Na1  1  0.019  0.485  0.485  1.0
  Na  Na2  1  0.485  0.019  0.485  1.0
  Na  Na3  1  0.755  0.755  0.755  1.0
  Ca  Ca4  1  0.012  0.012  0.467  1.0
  Ca  Ca5  1  0.467  0.012  0.012  1.0
  Ca  Ca6  1  0.012  0.467  0.012  1.0
  Ca  Ca7  1  0.998  0.998  0.998  1.0
  Si  Si8  1  0.719  0.719  0.259  1.0
  Si  Si9  1  0.259  0.719  0.719  1.0
  Si  Si10  1  0.719  0.259  0.719  1.0
  Si  Si11  1  0.284  0.284  0.738  1.0
  Si  Si12  1  0.738  0.284  0.284  1.0
  Si  Si13  1  0.284  0.738  0.284  1.0
  O  O14  1  0.797  0.797  0.437  1.0
  O  O15  1  0.437  0.797  0.797  1.0
  O  O16  1  0.797  0.437  0.797  1.0
  O  O17  1  0.207  0.207  0.563  1.0
  O  O18  1  0.563  0.207  0.207  1.0
  O  O19  1  0.207  0.563  0.207  1.0
  O  O20  1  0.792  0.792  0.072  1.0
  O  O21  1  0.072  0.792  0.792  1.0
  O  O22  1  0.792  0.072  0.792  1.0
  O  O23  1  0.210  0.210  0.926  1.0
  O  O24  1  0.926  0.210  0.210  1.0
  O  O25  1  0.210  0.926  0.210  1.0
  O  O26  1  0.250  0.752  0.501  1.0
  O  O27  1  0.501  0.250  0.752  1.0
  O  O28  1  0.752  0.501  0.250  1.0
  O  O29  1  0.501  0.752  0.250  1.0
  O  O30  1  0.250  0.501  0.752  1.0
  O  O31  1  0.752  0.250  0.501  1.0
[/CIF]
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The compound described by Na2Ca2Si3O9 crystallizes in the trigonal R3m space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(5) atoms. In the second Na site, Na(2) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form distorted NaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and  a faceface with one Ca(2)O6 octahedra. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form CaO6 octahedra that share corners with three equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and  a faceface with one Na(2)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), and two equivalent O(5) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ca(2)O6 octahedra, corners with two equivalent Na(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 39-48°. In the second Si site, Si(2) is bonded to one O(2), one O(4), and two equivalent O(5) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ca(2)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Ca(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Ca(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(2), one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to two equivalent Na(1), one Ca(1), one Si(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Ca2(SiO3)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.595
_cell_length_b   7.595
_cell_length_c   7.595
_cell_angle_alpha   88.790
_cell_angle_beta   88.790
_cell_angle_gamma   88.790
_symmetry_Int_Tables_number   1
_cell_volume   437.778
_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
  Na  Na0  1  0.485  0.485  0.019  1.0
  Na  Na1  1  0.019  0.485  0.485  1.0
  Na  Na2  1  0.485  0.019  0.485  1.0
  Na  Na3  1  0.755  0.755  0.755  1.0
  Ca  Ca4  1  0.012  0.012  0.467  1.0
  Ca  Ca5  1  0.467  0.012  0.012  1.0
  Ca  Ca6  1  0.012  0.467  0.012  1.0
  Ca  Ca7  1  0.998  0.998  0.998  1.0
  Si  Si8  1  0.719  0.719  0.259  1.0
  Si  Si9  1  0.259  0.719  0.719  1.0
  Si  Si10  1  0.719  0.259  0.719  1.0
  Si  Si11  1  0.284  0.284  0.738  1.0
  Si  Si12  1  0.738  0.284  0.284  1.0
  Si  Si13  1  0.284  0.738  0.284  1.0
  O  O14  1  0.797  0.797  0.437  1.0
  O  O15  1  0.437  0.797  0.797  1.0
  O  O16  1  0.797  0.437  0.797  1.0
  O  O17  1  0.207  0.207  0.563  1.0
  O  O18  1  0.563  0.207  0.207  1.0
  O  O19  1  0.207  0.563  0.207  1.0
  O  O20  1  0.792  0.792  0.072  1.0
  O  O21  1  0.072  0.792  0.792  1.0
  O  O22  1  0.792  0.072  0.792  1.0
  O  O23  1  0.210  0.210  0.926  1.0
  O  O24  1  0.926  0.210  0.210  1.0
  O  O25  1  0.210  0.926  0.210  1.0
  O  O26  1  0.250  0.752  0.501  1.0
  O  O27  1  0.501  0.250  0.752  1.0
  O  O28  1  0.752  0.501  0.250  1.0
  O  O29  1  0.501  0.752  0.250  1.0
  O  O30  1  0.250  0.501  0.752  1.0
  O  O31  1  0.752  0.250  0.501  1.0
[/CIF]
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