The structure described by KMg3(SiO3)4 crystallizes in the monoclinic C2/c space group. K(1) is bonded to four equivalent O(2), four equivalent O(4), and four equivalent O(6) atoms to form KO12 cuboctahedra that share edges with six equivalent K(1)O12 cuboctahedra, edges with six equivalent Si(1)O4 tetrahedra, and edges with six equivalent Si(2)O4 tetrahedra. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with three equivalent Mg(1)O6 octahedra, and edges with three equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with six equivalent Mg(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Si(2)O4 tetrahedra, and edges with three equivalent K(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 54-59°. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Si(1)O4 tetrahedra, and edges with three equivalent K(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 56-59°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(2) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Mg(2) and two equivalent Mg(1) atoms. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one Si(1), and one Si(2) atom. is represented by the CIF card [CIF]
data_KMg3(SiO3)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.294
_cell_length_b   5.294
_cell_length_c   20.792
_cell_angle_alpha   87.509
_cell_angle_beta   87.509
_cell_angle_gamma   119.716
_symmetry_Int_Tables_number   1
_cell_volume   504.246
_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  0.586  0.414  0.250  1.0
  K  K1  1  0.414  0.586  0.750  1.0
  Mg  Mg2  1  0.664  0.829  1.000  1.0
  Mg  Mg3  1  0.336  0.171  0.000  1.0
  Mg  Mg4  1  0.171  0.336  0.500  1.0
  Mg  Mg5  1  0.829  0.664  0.500  1.0
  Mg  Mg6  1  0.500  0.000  0.500  1.0
  Mg  Mg7  1  0.000  0.500  0.000  1.0
  Si  Si8  1  0.288  0.781  0.133  1.0
  Si  Si9  1  0.712  0.219  0.867  1.0
  Si  Si10  1  0.219  0.712  0.367  1.0
  Si  Si11  1  0.781  0.288  0.633  1.0
  Si  Si12  1  0.888  0.048  0.367  1.0
  Si  Si13  1  0.112  0.952  0.633  1.0
  Si  Si14  1  0.952  0.112  0.133  1.0
  Si  Si15  1  0.048  0.888  0.867  1.0
  O  O16  1  0.861  0.030  0.444  1.0
  O  O17  1  0.139  0.970  0.556  1.0
  O  O18  1  0.970  0.139  0.056  1.0
  O  O19  1  0.030  0.861  0.944  1.0
  O  O20  1  0.564  0.888  0.337  1.0
  O  O21  1  0.436  0.112  0.663  1.0
  O  O22  1  0.112  0.436  0.163  1.0
  O  O23  1  0.888  0.564  0.837  1.0
  O  O24  1  0.310  0.819  0.055  1.0
  O  O25  1  0.690  0.181  0.945  1.0
  O  O26  1  0.181  0.690  0.445  1.0
  O  O27  1  0.819  0.310  0.555  1.0
  O  O28  1  0.609  0.932  0.165  1.0
  O  O29  1  0.391  0.068  0.835  1.0
  O  O30  1  0.068  0.391  0.335  1.0
  O  O31  1  0.932  0.609  0.665  1.0
  O  O32  1  0.515  0.358  0.453  1.0
  O  O33  1  0.485  0.642  0.547  1.0
  O  O34  1  0.642  0.485  0.047  1.0
  O  O35  1  0.358  0.515  0.953  1.0
  O  O36  1  0.109  0.936  0.165  1.0
  O  O37  1  0.891  0.064  0.835  1.0
  O  O38  1  0.064  0.891  0.335  1.0
  O  O39  1  0.936  0.109  0.665  1.0
[/CIF]
.
The structure described by KMg3(SiO3)4 crystallizes in the monoclinic C2/c space group. K(1) is bonded to four equivalent O(2), four equivalent O(4), and four equivalent O(6) atoms to form KO12 cuboctahedra that share edges with six equivalent K(1)O12 cuboctahedra, edges with six equivalent Si(1)O4 tetrahedra, and edges with six equivalent Si(2)O4 tetrahedra. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with three equivalent Mg(1)O6 octahedra, and edges with three equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with six equivalent Mg(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Si(2)O4 tetrahedra, and edges with three equivalent K(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 54-59°. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Si(1)O4 tetrahedra, and edges with three equivalent K(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 56-59°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(2) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent K(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Mg(2) and two equivalent Mg(1) atoms. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one Si(1), and one Si(2) atom. is represented by the CIF card [CIF]
data_KMg3(SiO3)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.294
_cell_length_b   5.294
_cell_length_c   20.792
_cell_angle_alpha   87.509
_cell_angle_beta   87.509
_cell_angle_gamma   119.716
_symmetry_Int_Tables_number   1
_cell_volume   504.246
_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  0.586  0.414  0.250  1.0
  K  K1  1  0.414  0.586  0.750  1.0
  Mg  Mg2  1  0.664  0.829  1.000  1.0
  Mg  Mg3  1  0.336  0.171  0.000  1.0
  Mg  Mg4  1  0.171  0.336  0.500  1.0
  Mg  Mg5  1  0.829  0.664  0.500  1.0
  Mg  Mg6  1  0.500  0.000  0.500  1.0
  Mg  Mg7  1  0.000  0.500  0.000  1.0
  Si  Si8  1  0.288  0.781  0.133  1.0
  Si  Si9  1  0.712  0.219  0.867  1.0
  Si  Si10  1  0.219  0.712  0.367  1.0
  Si  Si11  1  0.781  0.288  0.633  1.0
  Si  Si12  1  0.888  0.048  0.367  1.0
  Si  Si13  1  0.112  0.952  0.633  1.0
  Si  Si14  1  0.952  0.112  0.133  1.0
  Si  Si15  1  0.048  0.888  0.867  1.0
  O  O16  1  0.861  0.030  0.444  1.0
  O  O17  1  0.139  0.970  0.556  1.0
  O  O18  1  0.970  0.139  0.056  1.0
  O  O19  1  0.030  0.861  0.944  1.0
  O  O20  1  0.564  0.888  0.337  1.0
  O  O21  1  0.436  0.112  0.663  1.0
  O  O22  1  0.112  0.436  0.163  1.0
  O  O23  1  0.888  0.564  0.837  1.0
  O  O24  1  0.310  0.819  0.055  1.0
  O  O25  1  0.690  0.181  0.945  1.0
  O  O26  1  0.181  0.690  0.445  1.0
  O  O27  1  0.819  0.310  0.555  1.0
  O  O28  1  0.609  0.932  0.165  1.0
  O  O29  1  0.391  0.068  0.835  1.0
  O  O30  1  0.068  0.391  0.335  1.0
  O  O31  1  0.932  0.609  0.665  1.0
  O  O32  1  0.515  0.358  0.453  1.0
  O  O33  1  0.485  0.642  0.547  1.0
  O  O34  1  0.642  0.485  0.047  1.0
  O  O35  1  0.358  0.515  0.953  1.0
  O  O36  1  0.109  0.936  0.165  1.0
  O  O37  1  0.891  0.064  0.835  1.0
  O  O38  1  0.064  0.891  0.335  1.0
  O  O39  1  0.936  0.109  0.665  1.0
[/CIF]
.