The crystal structure described by K4SrSi3O9 crystallizes in the orthorhombic Ama2 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 10-coordinate geometry to one O(5), one O(6), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. In the third K site, K(3) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(3), and two equivalent O(5) atoms. In the fourth K site, K(4) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form distorted KO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and faces with two equivalent Sr(1)O6 octahedra. Sr(1) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form SrO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and faces with two equivalent K(4)O6 octahedra. There are two 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 K(4)O6 octahedra, corners with two equivalent Sr(1)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 29-69°. In the second Si site, Si(2) is bonded to one O(5), one O(6), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with two equivalent K(4)O6 octahedra, corners with two equivalent Sr(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 3-80°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(2), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded in a 1-coordinate geometry to one K(1), one K(2), one K(4), one Sr(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one K(1), one K(3), one K(4), one Sr(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(3), two equivalent K(1), and two equivalent Si(1) atoms. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one K(1), one K(4), two equivalent K(3), one Sr(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one K(1), one K(4), two equivalent K(2), one Sr(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_K4Sr(SiO3)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.165
_cell_length_b   7.165
_cell_length_c   10.999
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   112.635
_symmetry_Int_Tables_number   1
_cell_volume   521.184
_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
  K  K0  1  0.342  0.765  0.750  1.0
  K  K1  1  0.945  0.055  0.000  1.0
  K  K2  1  0.501  0.499  0.000  1.0
  K  K3  1  0.235  0.658  0.250  1.0
  K  K4  1  0.219  0.228  0.750  1.0
  K  K5  1  0.501  0.499  0.500  1.0
  K  K6  1  0.772  0.781  0.250  1.0
  K  K7  1  0.945  0.055  0.500  1.0
  Sr  Sr8  1  0.725  0.255  0.750  1.0
  Sr  Sr9  1  0.745  0.275  0.250  1.0
  Si  Si10  1  0.409  0.980  0.031  1.0
  Si  Si11  1  0.020  0.591  0.969  1.0
  Si  Si12  1  0.020  0.591  0.531  1.0
  Si  Si13  1  0.260  0.189  0.250  1.0
  Si  Si14  1  0.811  0.740  0.750  1.0
  Si  Si15  1  0.409  0.980  0.469  1.0
  O  O16  1  0.946  0.729  0.871  1.0
  O  O17  1  0.027  0.400  0.603  1.0
  O  O18  1  0.887  0.553  0.090  1.0
  O  O19  1  0.271  0.054  0.129  1.0
  O  O20  1  0.271  0.054  0.371  1.0
  O  O21  1  0.260  0.740  0.000  1.0
  O  O22  1  0.447  0.113  0.590  1.0
  O  O23  1  0.447  0.113  0.910  1.0
  O  O24  1  0.599  0.548  0.750  1.0
  O  O25  1  0.260  0.740  0.500  1.0
  O  O26  1  0.600  0.973  0.103  1.0
  O  O27  1  0.043  0.201  0.250  1.0
  O  O28  1  0.799  0.957  0.750  1.0
  O  O29  1  0.452  0.401  0.250  1.0
  O  O30  1  0.887  0.553  0.410  1.0
  O  O31  1  0.027  0.400  0.897  1.0
  O  O32  1  0.600  0.973  0.397  1.0
  O  O33  1  0.946  0.729  0.629  1.0
[/CIF]
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The crystal structure described by K4SrSi3O9 crystallizes in the orthorhombic Ama2 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 10-coordinate geometry to one O(5), one O(6), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. In the third K site, K(3) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(3), and two equivalent O(5) atoms. In the fourth K site, K(4) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form distorted KO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and faces with two equivalent Sr(1)O6 octahedra. Sr(1) is bonded to one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms to form SrO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and faces with two equivalent K(4)O6 octahedra. There are two 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 K(4)O6 octahedra, corners with two equivalent Sr(1)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 29-69°. In the second Si site, Si(2) is bonded to one O(5), one O(6), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with two equivalent K(4)O6 octahedra, corners with two equivalent Sr(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 3-80°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(2), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded in a 1-coordinate geometry to one K(1), one K(2), one K(4), one Sr(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one K(1), one K(3), one K(4), one Sr(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(3), two equivalent K(1), and two equivalent Si(1) atoms. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one K(1), one K(4), two equivalent K(3), one Sr(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one K(1), one K(4), two equivalent K(2), one Sr(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_K4Sr(SiO3)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.165
_cell_length_b   7.165
_cell_length_c   10.999
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   112.635
_symmetry_Int_Tables_number   1
_cell_volume   521.184
_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
  K  K0  1  0.342  0.765  0.750  1.0
  K  K1  1  0.945  0.055  0.000  1.0
  K  K2  1  0.501  0.499  0.000  1.0
  K  K3  1  0.235  0.658  0.250  1.0
  K  K4  1  0.219  0.228  0.750  1.0
  K  K5  1  0.501  0.499  0.500  1.0
  K  K6  1  0.772  0.781  0.250  1.0
  K  K7  1  0.945  0.055  0.500  1.0
  Sr  Sr8  1  0.725  0.255  0.750  1.0
  Sr  Sr9  1  0.745  0.275  0.250  1.0
  Si  Si10  1  0.409  0.980  0.031  1.0
  Si  Si11  1  0.020  0.591  0.969  1.0
  Si  Si12  1  0.020  0.591  0.531  1.0
  Si  Si13  1  0.260  0.189  0.250  1.0
  Si  Si14  1  0.811  0.740  0.750  1.0
  Si  Si15  1  0.409  0.980  0.469  1.0
  O  O16  1  0.946  0.729  0.871  1.0
  O  O17  1  0.027  0.400  0.603  1.0
  O  O18  1  0.887  0.553  0.090  1.0
  O  O19  1  0.271  0.054  0.129  1.0
  O  O20  1  0.271  0.054  0.371  1.0
  O  O21  1  0.260  0.740  0.000  1.0
  O  O22  1  0.447  0.113  0.590  1.0
  O  O23  1  0.447  0.113  0.910  1.0
  O  O24  1  0.599  0.548  0.750  1.0
  O  O25  1  0.260  0.740  0.500  1.0
  O  O26  1  0.600  0.973  0.103  1.0
  O  O27  1  0.043  0.201  0.250  1.0
  O  O28  1  0.799  0.957  0.750  1.0
  O  O29  1  0.452  0.401  0.250  1.0
  O  O30  1  0.887  0.553  0.410  1.0
  O  O31  1  0.027  0.400  0.897  1.0
  O  O32  1  0.600  0.973  0.397  1.0
  O  O33  1  0.946  0.729  0.629  1.0
[/CIF]
.