The compound described by CaSi2O5 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 9-coordinate geometry to one O(10), one O(2), one O(3), one O(5), one O(9), two equivalent O(4), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(2), one O(5), one O(6), one O(9), and two equivalent O(8) atoms. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(2), one O(4), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(4)O6 octahedra,  a cornercorner with one Si(5)O6 octahedra, and  a cornercorner with one Si(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 43-55°. In the second Si site, Si(2) is bonded to one O(1), one O(5), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(4)O6 octahedra,  a cornercorner with one Si(5)O6 octahedra, and corners with two equivalent Si(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 36-57°. In the third Si site, Si(3) is bonded to one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form SiO5 trigonal bipyramids that share  a cornercorner with one Si(4)O6 octahedra,  a cornercorner with one Si(5)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 36°. In the fourth Si site, Si(4) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(9) atoms to form SiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O5 trigonal bipyramids. In the fifth Si site, Si(5) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form SiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O5 trigonal bipyramids. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(2), one Si(2), and one Si(5) atom. In the second O site, O(2) is bonded to one Ca(1), one Ca(2), one Si(1), and one Si(5) atom to form distorted corner-sharing OCa2Si2 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Si(3), and one Si(5) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to two equivalent Ca(1), one Si(1), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ca(1), one Ca(2), one Si(2), and one Si(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(2), one Si(3), and one Si(4) atom. In the seventh O site, O(7) is bonded to two equivalent Ca(1), one Si(2), and one Si(3) atom to form a mixture of distorted corner and edge-sharing OCa2Si2 tetrahedra. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Si(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 Si(2), and one Si(4) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Si(1) atom. is represented by the CIF card [CIF]
data_CaSi2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.627
_cell_length_b   7.313
_cell_length_c   7.628
_cell_angle_alpha   69.508
_cell_angle_beta   81.406
_cell_angle_gamma   84.865
_symmetry_Int_Tables_number   1
_cell_volume   342.118
_cell_formula_units_Z   4
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  0.610  0.029  0.214  1.0
  Ca  Ca1  1  0.390  0.971  0.786  1.0
  Ca  Ca2  1  0.816  0.458  0.321  1.0
  Ca  Ca3  1  0.184  0.542  0.679  1.0
  Si  Si4  1  0.661  0.684  0.579  1.0
  Si  Si5  1  0.339  0.316  0.421  1.0
  Si  Si6  1  0.126  0.199  0.070  1.0
  Si  Si7  1  0.874  0.801  0.930  1.0
  Si  Si8  1  0.802  0.247  0.779  1.0
  Si  Si9  1  0.198  0.753  0.221  1.0
  Si  Si10  1  0.000  0.000  0.500  1.0
  Si  Si11  1  0.500  0.500  0.000  1.0
  O  O12  1  0.752  0.601  0.986  1.0
  O  O13  1  0.248  0.399  0.014  1.0
  O  O14  1  0.476  0.652  0.758  1.0
  O  O15  1  0.524  0.348  0.242  1.0
  O  O16  1  0.621  0.305  0.935  1.0
  O  O17  1  0.379  0.695  0.065  1.0
  O  O18  1  0.249  0.100  0.460  1.0
  O  O19  1  0.751  0.900  0.540  1.0
  O  O20  1  0.022  0.227  0.878  1.0
  O  O21  1  0.978  0.773  0.122  1.0
  O  O22  1  0.884  0.190  0.581  1.0
  O  O23  1  0.116  0.810  0.419  1.0
  O  O24  1  0.281  0.004  0.098  1.0
  O  O25  1  0.719  0.996  0.902  1.0
  O  O26  1  0.173  0.502  0.365  1.0
  O  O27  1  0.827  0.498  0.635  1.0
  O  O28  1  0.050  0.842  0.744  1.0
  O  O29  1  0.950  0.158  0.256  1.0
  O  O30  1  0.426  0.301  0.612  1.0
  O  O31  1  0.574  0.699  0.388  1.0
[/CIF]
.
The compound described by CaSi2O5 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 9-coordinate geometry to one O(10), one O(2), one O(3), one O(5), one O(9), two equivalent O(4), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(2), one O(5), one O(6), one O(9), and two equivalent O(8) atoms. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(2), one O(4), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(4)O6 octahedra,  a cornercorner with one Si(5)O6 octahedra, and  a cornercorner with one Si(3)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 43-55°. In the second Si site, Si(2) is bonded to one O(1), one O(5), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(4)O6 octahedra,  a cornercorner with one Si(5)O6 octahedra, and corners with two equivalent Si(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 36-57°. In the third Si site, Si(3) is bonded to one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form SiO5 trigonal bipyramids that share  a cornercorner with one Si(4)O6 octahedra,  a cornercorner with one Si(5)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 36°. In the fourth Si site, Si(4) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(9) atoms to form SiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O5 trigonal bipyramids. In the fifth Si site, Si(5) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form SiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O5 trigonal bipyramids. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(2), one Si(2), and one Si(5) atom. In the second O site, O(2) is bonded to one Ca(1), one Ca(2), one Si(1), and one Si(5) atom to form distorted corner-sharing OCa2Si2 tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Si(3), and one Si(5) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to two equivalent Ca(1), one Si(1), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ca(1), one Ca(2), one Si(2), and one Si(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(2), one Si(3), and one Si(4) atom. In the seventh O site, O(7) is bonded to two equivalent Ca(1), one Si(2), and one Si(3) atom to form a mixture of distorted corner and edge-sharing OCa2Si2 tetrahedra. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to two equivalent Ca(2), one Si(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 Si(2), and one Si(4) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one Si(1) atom. is represented by the CIF card [CIF]
data_CaSi2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.627
_cell_length_b   7.313
_cell_length_c   7.628
_cell_angle_alpha   69.508
_cell_angle_beta   81.406
_cell_angle_gamma   84.865
_symmetry_Int_Tables_number   1
_cell_volume   342.118
_cell_formula_units_Z   4
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  0.610  0.029  0.214  1.0
  Ca  Ca1  1  0.390  0.971  0.786  1.0
  Ca  Ca2  1  0.816  0.458  0.321  1.0
  Ca  Ca3  1  0.184  0.542  0.679  1.0
  Si  Si4  1  0.661  0.684  0.579  1.0
  Si  Si5  1  0.339  0.316  0.421  1.0
  Si  Si6  1  0.126  0.199  0.070  1.0
  Si  Si7  1  0.874  0.801  0.930  1.0
  Si  Si8  1  0.802  0.247  0.779  1.0
  Si  Si9  1  0.198  0.753  0.221  1.0
  Si  Si10  1  0.000  0.000  0.500  1.0
  Si  Si11  1  0.500  0.500  0.000  1.0
  O  O12  1  0.752  0.601  0.986  1.0
  O  O13  1  0.248  0.399  0.014  1.0
  O  O14  1  0.476  0.652  0.758  1.0
  O  O15  1  0.524  0.348  0.242  1.0
  O  O16  1  0.621  0.305  0.935  1.0
  O  O17  1  0.379  0.695  0.065  1.0
  O  O18  1  0.249  0.100  0.460  1.0
  O  O19  1  0.751  0.900  0.540  1.0
  O  O20  1  0.022  0.227  0.878  1.0
  O  O21  1  0.978  0.773  0.122  1.0
  O  O22  1  0.884  0.190  0.581  1.0
  O  O23  1  0.116  0.810  0.419  1.0
  O  O24  1  0.281  0.004  0.098  1.0
  O  O25  1  0.719  0.996  0.902  1.0
  O  O26  1  0.173  0.502  0.365  1.0
  O  O27  1  0.827  0.498  0.635  1.0
  O  O28  1  0.050  0.842  0.744  1.0
  O  O29  1  0.950  0.158  0.256  1.0
  O  O30  1  0.426  0.301  0.612  1.0
  O  O31  1  0.574  0.699  0.388  1.0
[/CIF]
.