The compound described by Ca2PbSi3O9 crystallizes in the triclinic P-1 space group. 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(4), one O(7), one O(9), two equivalent O(5), and two equivalent O(6) atoms. In the second Ca site, Ca(2) is bonded to one O(1), one O(2), one O(5), one O(9), and two equivalent O(8) atoms to form CaO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(3)O4 tetrahedra, and  an edgeedge with one Ca(2)O6 octahedra. Pb(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(6), one O(8), and one O(9) atom. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Ca(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-60°. In the second Si site, Si(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. In the third Si site, Si(3) is bonded to one O(3), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share corners with three equivalent Ca(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-61°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), one Pb(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(2), one Pb(1), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded to one Ca(2), two equivalent Ca(1), and one Si(2) atom to form distorted edge-sharing OCa3Si tetrahedra. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to two equivalent Ca(1), one Pb(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Pb(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Pb(1), and one Si(3) atom. is represented by the CIF file [CIF]
data_Ca2Si3PbO9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.782
_cell_length_b   6.831
_cell_length_c   9.657
_cell_angle_alpha   82.881
_cell_angle_beta   69.640
_cell_angle_gamma   76.758
_symmetry_Int_Tables_number   1
_cell_volume   407.773
_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  0.764  0.728  0.505  1.0
  Ca  Ca1  1  0.236  0.272  0.495  1.0
  Ca  Ca2  1  0.930  0.558  0.832  1.0
  Ca  Ca3  1  0.070  0.442  0.168  1.0
  Si  Si4  1  0.158  0.904  0.219  1.0
  Si  Si5  1  0.842  0.096  0.781  1.0
  Si  Si6  1  0.281  0.767  0.484  1.0
  Si  Si7  1  0.719  0.233  0.516  1.0
  Si  Si8  1  0.515  0.562  0.202  1.0
  Si  Si9  1  0.485  0.438  0.798  1.0
  Pb  Pb10  1  0.281  0.907  0.842  1.0
  Pb  Pb11  1  0.719  0.093  0.158  1.0
  O  O12  1  0.975  0.770  0.256  1.0
  O  O13  1  0.025  0.230  0.744  1.0
  O  O14  1  0.906  0.892  0.874  1.0
  O  O15  1  0.094  0.108  0.126  1.0
  O  O16  1  0.396  0.767  0.124  1.0
  O  O17  1  0.604  0.233  0.876  1.0
  O  O18  1  0.194  0.954  0.373  1.0
  O  O19  1  0.806  0.046  0.627  1.0
  O  O20  1  0.105  0.626  0.560  1.0
  O  O21  1  0.895  0.374  0.440  1.0
  O  O22  1  0.361  0.872  0.590  1.0
  O  O23  1  0.639  0.128  0.410  1.0
  O  O24  1  0.507  0.641  0.362  1.0
  O  O25  1  0.493  0.359  0.638  1.0
  O  O26  1  0.240  0.522  0.902  1.0
  O  O27  1  0.760  0.478  0.098  1.0
  O  O28  1  0.627  0.613  0.759  1.0
  O  O29  1  0.373  0.387  0.241  1.0
[/CIF]
.
The compound described by Ca2PbSi3O9 crystallizes in the triclinic P-1 space group. 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(4), one O(7), one O(9), two equivalent O(5), and two equivalent O(6) atoms. In the second Ca site, Ca(2) is bonded to one O(1), one O(2), one O(5), one O(9), and two equivalent O(8) atoms to form CaO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(3)O4 tetrahedra, and  an edgeedge with one Ca(2)O6 octahedra. Pb(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(6), one O(8), and one O(9) atom. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Ca(2)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-60°. In the second Si site, Si(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. In the third Si site, Si(3) is bonded to one O(3), one O(7), one O(8), and one O(9) atom to form SiO4 tetrahedra that share corners with three equivalent Ca(2)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-61°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), one Pb(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(2), one Pb(1), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded to one Ca(2), two equivalent Ca(1), and one Si(2) atom to form distorted edge-sharing OCa3Si tetrahedra. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to two equivalent Ca(1), one Pb(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Pb(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Pb(1), and one Si(3) atom. is represented by the CIF file [CIF]
data_Ca2Si3PbO9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.782
_cell_length_b   6.831
_cell_length_c   9.657
_cell_angle_alpha   82.881
_cell_angle_beta   69.640
_cell_angle_gamma   76.758
_symmetry_Int_Tables_number   1
_cell_volume   407.773
_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  0.764  0.728  0.505  1.0
  Ca  Ca1  1  0.236  0.272  0.495  1.0
  Ca  Ca2  1  0.930  0.558  0.832  1.0
  Ca  Ca3  1  0.070  0.442  0.168  1.0
  Si  Si4  1  0.158  0.904  0.219  1.0
  Si  Si5  1  0.842  0.096  0.781  1.0
  Si  Si6  1  0.281  0.767  0.484  1.0
  Si  Si7  1  0.719  0.233  0.516  1.0
  Si  Si8  1  0.515  0.562  0.202  1.0
  Si  Si9  1  0.485  0.438  0.798  1.0
  Pb  Pb10  1  0.281  0.907  0.842  1.0
  Pb  Pb11  1  0.719  0.093  0.158  1.0
  O  O12  1  0.975  0.770  0.256  1.0
  O  O13  1  0.025  0.230  0.744  1.0
  O  O14  1  0.906  0.892  0.874  1.0
  O  O15  1  0.094  0.108  0.126  1.0
  O  O16  1  0.396  0.767  0.124  1.0
  O  O17  1  0.604  0.233  0.876  1.0
  O  O18  1  0.194  0.954  0.373  1.0
  O  O19  1  0.806  0.046  0.627  1.0
  O  O20  1  0.105  0.626  0.560  1.0
  O  O21  1  0.895  0.374  0.440  1.0
  O  O22  1  0.361  0.872  0.590  1.0
  O  O23  1  0.639  0.128  0.410  1.0
  O  O24  1  0.507  0.641  0.362  1.0
  O  O25  1  0.493  0.359  0.638  1.0
  O  O26  1  0.240  0.522  0.902  1.0
  O  O27  1  0.760  0.478  0.098  1.0
  O  O28  1  0.627  0.613  0.759  1.0
  O  O29  1  0.373  0.387  0.241  1.0
[/CIF]
.