The material structure described by K2Si2O5 crystallizes in the monoclinic Cc space group. There are six inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to one O(10), one O(15), one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the second K site, K(2) is bonded in a 8-coordinate geometry to one O(1), one O(11), one O(12), one O(13), one O(15), one O(2), one O(8), and one O(9) atom. In the third K site, K(3) is bonded in a 7-coordinate geometry to one O(10), one O(12), one O(2), one O(5), one O(6), and two equivalent O(3) atoms. In the fourth K site, K(4) is bonded to one O(12), one O(13), one O(2), one O(5), one O(6), and one O(7) atom to form KO6 octahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra, and  a cornercorner with one Si(6)O4 tetrahedra. In the fifth K site, K(5) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(13), one O(14), one O(6), and one O(7) atom. In the sixth K site, K(6) is bonded in a 7-coordinate geometry to one O(10), one O(13), one O(2), one O(4), one O(5), one O(7), and one O(9) atom. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(11), one O(13), and one O(14) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(6)O4 tetrahedra. The corner-sharing octahedral tilt angles are 18°. In the second Si site, Si(2) is bonded to one O(1), one O(14), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(5)O4 tetrahedra. The corner-sharing octahedral tilt angles are 28°. In the third Si site, Si(3) is bonded to one O(12), one O(4), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles are 32°. In the fourth Si site, Si(4) is bonded to one O(15), one O(4), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(5)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 1°. In the fifth Si site, Si(5) is bonded to one O(1), one O(15), one O(2), and one O(3) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  a cornercorner with one Si(6)O4 tetrahedra. The corner-sharing octahedral tilt angles are 16°. In the sixth Si site, Si(6) is bonded to one O(10), one O(11), one O(3), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(5)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one K(2), one K(5), one Si(2), and one Si(5) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(2), one K(3), one K(4), one K(6), and one Si(5) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one K(1), two equivalent K(3), one Si(5), and one Si(6) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(6), one Si(3), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one K(1), one K(3), one K(4), one K(6), and one Si(6) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one K(1), one K(3), one K(4), one K(5), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(1), one K(4), one K(5), one K(6), and one Si(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(2), one Si(2), and one Si(3) atom. In the ninth O site, O(9) is bonded in a distorted bent 150 degrees geometry to one K(2), one K(6), one Si(3), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(3), one K(6), one Si(1), and one Si(6) atom. In the eleventh O site, O(11) is bonded in a 2-coordinate geometry to one K(2), one K(5), one Si(1), and one Si(6) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to one K(2), one K(3), one K(4), and one Si(3) atom. In the thirteenth O site, O(13) is bonded in a distorted single-bond geometry to one K(2), one K(4), one K(5), one K(6), and one Si(1) atom. In the fourteenth O site, O(14) is bonded in a distorted linear geometry to one K(5), one Si(1), and one Si(2) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one K(1), one K(2), one Si(4), and one Si(5) atom. is represented by the CIF card [CIF]
data_K2Si2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.959
_cell_length_b   9.959
_cell_length_c   9.953
_cell_angle_alpha   68.694
_cell_angle_beta   68.694
_cell_angle_gamma   68.849
_symmetry_Int_Tables_number   1
_cell_volume   826.607
_cell_formula_units_Z   6
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
  K  K0  1  0.616  0.099  0.930  1.0
  K  K1  1  0.099  0.616  0.430  1.0
  K  K2  1  0.285  0.838  0.623  1.0
  K  K3  1  0.838  0.285  0.123  1.0
  K  K4  1  0.235  0.206  0.022  1.0
  K  K5  1  0.206  0.235  0.522  1.0
  K  K6  1  0.436  0.961  0.784  1.0
  K  K7  1  0.961  0.436  0.284  1.0
  K  K8  1  0.637  0.683  0.967  1.0
  K  K9  1  0.683  0.637  0.467  1.0
  K  K10  1  0.678  0.143  0.519  1.0
  K  K11  1  0.143  0.678  0.019  1.0
  Si  Si12  1  0.515  0.484  0.325  1.0
  Si  Si13  1  0.844  0.386  0.737  1.0
  Si  Si14  1  0.386  0.844  0.237  1.0
  Si  Si15  1  0.994  0.045  0.876  1.0
  Si  Si16  1  0.045  0.994  0.376  1.0
  Si  Si17  1  0.874  0.909  0.222  1.0
  Si  Si18  1  0.909  0.874  0.722  1.0
  Si  Si19  1  0.026  0.522  0.825  1.0
  Si  Si20  1  0.522  0.026  0.325  1.0
  Si  Si21  1  0.396  0.361  0.166  1.0
  Si  Si22  1  0.361  0.396  0.666  1.0
  Si  Si23  1  0.484  0.515  0.825  1.0
  O  O24  1  0.881  0.476  0.825  1.0
  O  O25  1  0.032  0.482  0.991  1.0
  O  O26  1  0.482  0.032  0.491  1.0
  O  O27  1  0.433  0.176  0.218  1.0
  O  O28  1  0.176  0.433  0.718  1.0
  O  O29  1  0.936  0.923  0.850  1.0
  O  O30  1  0.923  0.936  0.350  1.0
  O  O31  1  0.234  0.442  0.243  1.0
  O  O32  1  0.442  0.234  0.743  1.0
  O  O33  1  0.930  0.417  0.567  1.0
  O  O34  1  0.417  0.930  0.067  1.0
  O  O35  1  0.904  0.737  0.246  1.0
  O  O36  1  0.210  0.871  0.341  1.0
  O  O37  1  0.871  0.210  0.841  1.0
  O  O38  1  0.998  0.968  0.559  1.0
  O  O39  1  0.968  0.998  0.059  1.0
  O  O40  1  0.393  0.430  0.483  1.0
  O  O41  1  0.430  0.393  0.983  1.0
  O  O42  1  0.405  0.524  0.700  1.0
  O  O43  1  0.524  0.405  0.200  1.0
  O  O44  1  0.042  0.160  0.285  1.0
  O  O45  1  0.160  0.042  0.785  1.0
  O  O46  1  0.678  0.442  0.341  1.0
  O  O47  1  0.442  0.678  0.841  1.0
  O  O48  1  0.444  0.663  0.262  1.0
  O  O49  1  0.663  0.444  0.762  1.0
  O  O50  1  0.476  0.881  0.325  1.0
  O  O51  1  0.699  0.009  0.233  1.0
  O  O52  1  0.009  0.699  0.733  1.0
  O  O53  1  0.737  0.904  0.746  1.0
[/CIF]
.
The material structure described by K2Si2O5 crystallizes in the monoclinic Cc space group. There are six inequivalent K sites. In the first K site, K(1) is bonded in a 8-coordinate geometry to one O(10), one O(15), one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the second K site, K(2) is bonded in a 8-coordinate geometry to one O(1), one O(11), one O(12), one O(13), one O(15), one O(2), one O(8), and one O(9) atom. In the third K site, K(3) is bonded in a 7-coordinate geometry to one O(10), one O(12), one O(2), one O(5), one O(6), and two equivalent O(3) atoms. In the fourth K site, K(4) is bonded to one O(12), one O(13), one O(2), one O(5), one O(6), and one O(7) atom to form KO6 octahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra, and  a cornercorner with one Si(6)O4 tetrahedra. In the fifth K site, K(5) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(13), one O(14), one O(6), and one O(7) atom. In the sixth K site, K(6) is bonded in a 7-coordinate geometry to one O(10), one O(13), one O(2), one O(4), one O(5), one O(7), and one O(9) atom. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(11), one O(13), and one O(14) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(6)O4 tetrahedra. The corner-sharing octahedral tilt angles are 18°. In the second Si site, Si(2) is bonded to one O(1), one O(14), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(5)O4 tetrahedra. The corner-sharing octahedral tilt angles are 28°. In the third Si site, Si(3) is bonded to one O(12), one O(4), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles are 32°. In the fourth Si site, Si(4) is bonded to one O(15), one O(4), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(5)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 1°. In the fifth Si site, Si(5) is bonded to one O(1), one O(15), one O(2), and one O(3) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  a cornercorner with one Si(6)O4 tetrahedra. The corner-sharing octahedral tilt angles are 16°. In the sixth Si site, Si(6) is bonded to one O(10), one O(11), one O(3), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one K(4)O6 octahedra,  a cornercorner with one Si(5)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one K(2), one K(5), one Si(2), and one Si(5) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(2), one K(3), one K(4), one K(6), and one Si(5) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one K(1), two equivalent K(3), one Si(5), and one Si(6) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(6), one Si(3), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one K(1), one K(3), one K(4), one K(6), and one Si(6) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one K(1), one K(3), one K(4), one K(5), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one K(1), one K(4), one K(5), one K(6), and one Si(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(2), one Si(2), and one Si(3) atom. In the ninth O site, O(9) is bonded in a distorted bent 150 degrees geometry to one K(2), one K(6), one Si(3), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(3), one K(6), one Si(1), and one Si(6) atom. In the eleventh O site, O(11) is bonded in a 2-coordinate geometry to one K(2), one K(5), one Si(1), and one Si(6) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to one K(2), one K(3), one K(4), and one Si(3) atom. In the thirteenth O site, O(13) is bonded in a distorted single-bond geometry to one K(2), one K(4), one K(5), one K(6), and one Si(1) atom. In the fourteenth O site, O(14) is bonded in a distorted linear geometry to one K(5), one Si(1), and one Si(2) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one K(1), one K(2), one Si(4), and one Si(5) atom. is represented by the CIF card [CIF]
data_K2Si2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.959
_cell_length_b   9.959
_cell_length_c   9.953
_cell_angle_alpha   68.694
_cell_angle_beta   68.694
_cell_angle_gamma   68.849
_symmetry_Int_Tables_number   1
_cell_volume   826.607
_cell_formula_units_Z   6
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
  K  K0  1  0.616  0.099  0.930  1.0
  K  K1  1  0.099  0.616  0.430  1.0
  K  K2  1  0.285  0.838  0.623  1.0
  K  K3  1  0.838  0.285  0.123  1.0
  K  K4  1  0.235  0.206  0.022  1.0
  K  K5  1  0.206  0.235  0.522  1.0
  K  K6  1  0.436  0.961  0.784  1.0
  K  K7  1  0.961  0.436  0.284  1.0
  K  K8  1  0.637  0.683  0.967  1.0
  K  K9  1  0.683  0.637  0.467  1.0
  K  K10  1  0.678  0.143  0.519  1.0
  K  K11  1  0.143  0.678  0.019  1.0
  Si  Si12  1  0.515  0.484  0.325  1.0
  Si  Si13  1  0.844  0.386  0.737  1.0
  Si  Si14  1  0.386  0.844  0.237  1.0
  Si  Si15  1  0.994  0.045  0.876  1.0
  Si  Si16  1  0.045  0.994  0.376  1.0
  Si  Si17  1  0.874  0.909  0.222  1.0
  Si  Si18  1  0.909  0.874  0.722  1.0
  Si  Si19  1  0.026  0.522  0.825  1.0
  Si  Si20  1  0.522  0.026  0.325  1.0
  Si  Si21  1  0.396  0.361  0.166  1.0
  Si  Si22  1  0.361  0.396  0.666  1.0
  Si  Si23  1  0.484  0.515  0.825  1.0
  O  O24  1  0.881  0.476  0.825  1.0
  O  O25  1  0.032  0.482  0.991  1.0
  O  O26  1  0.482  0.032  0.491  1.0
  O  O27  1  0.433  0.176  0.218  1.0
  O  O28  1  0.176  0.433  0.718  1.0
  O  O29  1  0.936  0.923  0.850  1.0
  O  O30  1  0.923  0.936  0.350  1.0
  O  O31  1  0.234  0.442  0.243  1.0
  O  O32  1  0.442  0.234  0.743  1.0
  O  O33  1  0.930  0.417  0.567  1.0
  O  O34  1  0.417  0.930  0.067  1.0
  O  O35  1  0.904  0.737  0.246  1.0
  O  O36  1  0.210  0.871  0.341  1.0
  O  O37  1  0.871  0.210  0.841  1.0
  O  O38  1  0.998  0.968  0.559  1.0
  O  O39  1  0.968  0.998  0.059  1.0
  O  O40  1  0.393  0.430  0.483  1.0
  O  O41  1  0.430  0.393  0.983  1.0
  O  O42  1  0.405  0.524  0.700  1.0
  O  O43  1  0.524  0.405  0.200  1.0
  O  O44  1  0.042  0.160  0.285  1.0
  O  O45  1  0.160  0.042  0.785  1.0
  O  O46  1  0.678  0.442  0.341  1.0
  O  O47  1  0.442  0.678  0.841  1.0
  O  O48  1  0.444  0.663  0.262  1.0
  O  O49  1  0.663  0.444  0.762  1.0
  O  O50  1  0.476  0.881  0.325  1.0
  O  O51  1  0.699  0.009  0.233  1.0
  O  O52  1  0.009  0.699  0.733  1.0
  O  O53  1  0.737  0.904  0.746  1.0
[/CIF]
.