The crystal structure described by Si2Sb15O28 crystallizes in the triclinic P1 space group. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one O(11), one O(22), one O(3), and one O(4) atom. In the second Si site, Si(2) is bonded to one O(15), one O(16), one O(25), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Sb(1)O5 square pyramid and  a cornercorner with one Sb(11)O5 square pyramid. There are fifteen inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to one O(21), one O(25), one O(27), one O(5), and one O(6) atom to form SbO5 square pyramids that share  a cornercorner with one Si(2)O4 tetrahedra. In the second Sb site, Sb(2) is bonded in a 4-coordinate geometry to one O(1), one O(14), one O(15), and one O(3) atom. In the third Sb site, Sb(3) is bonded in a distorted T-shaped geometry to one O(2), one O(23), and one O(24) atom. In the fourth Sb site, Sb(4) is bonded in a distorted T-shaped geometry to one O(2), one O(20), and one O(24) atom. In the fifth Sb site, Sb(5) is bonded in a distorted T-shaped geometry to one O(17), one O(22), and one O(6) atom. In the sixth Sb site, Sb(6) is bonded in a 3-coordinate geometry to one O(13), one O(19), and one O(28) atom. In the seventh Sb site, Sb(7) is bonded in a distorted rectangular see-saw-like geometry to one O(10), one O(11), one O(12), and one O(16) atom. In the eighth Sb site, Sb(8) is bonded in a rectangular see-saw-like geometry to one O(10), one O(14), one O(18), and one O(4) atom. In the ninth Sb site, Sb(9) is bonded in a distorted T-shaped geometry to one O(10), one O(26), and one O(9) atom. In the tenth Sb site, Sb(10) is bonded in a 4-coordinate geometry to one O(18), one O(25), one O(27), and one O(3) atom. In the eleventh Sb site, Sb(11) is bonded to one O(1), one O(12), one O(15), one O(26), and one O(28) atom to form distorted SbO5 square pyramids that share  a cornercorner with one Si(2)O4 tetrahedra. In the twelfth Sb site, Sb(12) is bonded in a distorted trigonal non-coplanar geometry to one O(17), one O(21), and one O(9) atom. In the thirteenth Sb site, Sb(13) is bonded in a distorted T-shaped geometry to one O(5), one O(7), and one O(8) atom. In the fourteenth Sb site, Sb(14) is bonded in a distorted trigonal non-coplanar geometry to one O(19), one O(20), and one O(8) atom. In the fifteenth Sb site, Sb(15) is bonded in a distorted trigonal non-coplanar geometry to one O(13), one O(23), and one O(7) atom. There are twenty-eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Sb(11) and one Sb(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Sb(3) and one Sb(4) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Si(1), one Sb(10), and one Sb(2) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(1) and one Sb(8) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Sb(1) and one Sb(13) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Sb(1) and one Sb(5) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Sb(13) and one Sb(15) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Sb(13) and one Sb(14) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Si(2), one Sb(12), and one Sb(9) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Sb(7), one Sb(8), and one Sb(9) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one Si(1) and one Sb(7) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one Sb(11) and one Sb(7) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one Sb(15) and one Sb(6) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one Sb(2) and one Sb(8) atom. In the fifteenth O site, O(15) is bonded in a 3-coordinate geometry to one Si(2), one Sb(11), and one Sb(2) atom. In the sixteenth O site, O(16) is bonded in a bent 150 degrees geometry to one Si(2) and one Sb(7) atom. In the seventeenth O site, O(17) is bonded in a bent 150 degrees geometry to one Sb(12) and one Sb(5) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Sb(10) and one Sb(8) atom. In the nineteenth O site, O(19) is bonded in a bent 150 degrees geometry to one Sb(14) and one Sb(6) atom. In the twentieth O site, O(20) is bonded in a bent 150 degrees geometry to one Sb(14) and one Sb(4) atom. In the twenty-first O site, O(21) is bonded in a bent 120 degrees geometry to one Sb(1) and one Sb(12) atom. In the twenty-second O site, O(22) is bonded in a linear geometry to one Si(1) and one Sb(5) atom. In the twenty-third O site, O(23) is bonded in a bent 150 degrees geometry to one Sb(15) and one Sb(3) atom. In the twenty-fourth O site, O(24) is bonded in a bent 150 degrees geometry to one Sb(3) and one Sb(4) atom. In the twenty-fifth O site, O(25) is bonded in a 1-coordinate geometry to one Si(2), one Sb(1), and one Sb(10) atom. In the twenty-sixth O site, O(26) is bonded in a bent 150 degrees geometry to one Sb(11) and one Sb(9) atom. In the twenty-seventh O site, O(27) is bonded in a water-like geometry to one Sb(1) and one Sb(10) atom. In the twenty-eighth O site, O(28) is bonded in a bent 120 degrees geometry to one Sb(11) and one Sb(6) atom. is represented by the CIF file [CIF]
data_Si2Sb15O28
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.027
_cell_length_b   9.403
_cell_length_c   14.279
_cell_angle_alpha   90.374
_cell_angle_beta   102.118
_cell_angle_gamma   97.003
_symmetry_Int_Tables_number   1
_cell_volume   915.161
_cell_formula_units_Z   1
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
  Si  Si0  1  0.147  0.616  0.996  1.0
  Si  Si1  1  0.764  0.296  0.992  1.0
  Sb  Sb2  1  0.897  0.358  0.250  1.0
  Sb  Sb3  1  0.664  0.651  0.894  1.0
  Sb  Sb4  1  0.408  0.680  0.434  1.0
  Sb  Sb5  1  0.965  0.677  0.560  1.0
  Sb  Sb6  1  0.377  0.411  0.190  1.0
  Sb  Sb7  1  0.394  0.106  0.577  1.0
  Sb  Sb8  1  0.141  0.328  0.873  1.0
  Sb  Sb9  1  0.036  0.938  1.000  1.0
  Sb  Sb10  1  0.453  0.005  0.869  1.0
  Sb  Sb11  1  0.800  0.653  0.131  1.0
  Sb  Sb12  1  0.642  0.351  0.759  1.0
  Sb  Sb13  1  0.535  0.073  0.125  1.0
  Sb  Sb14  1  0.838  0.105  0.419  1.0
  Sb  Sb15  1  0.904  0.032  0.666  1.0
  Sb  Sb16  1  0.267  0.031  0.330  1.0
  O  O17  1  0.662  0.563  0.765  1.0
  O  O18  1  0.223  0.736  0.515  1.0
  O  O19  1  0.908  0.600  0.003  1.0
  O  O20  1  0.227  0.788  0.004  1.0
  O  O21  1  0.959  0.304  0.387  1.0
  O  O22  1  0.145  0.309  0.226  1.0
  O  O23  1  0.038  0.988  0.388  1.0
  O  O24  1  0.979  0.139  0.556  1.0
  O  O25  1  0.635  0.130  0.994  1.0
  O  O26  1  0.215  0.058  0.896  1.0
  O  O27  1  0.146  0.545  0.892  1.0
  O  O28  1  0.911  0.323  0.762  1.0
  O  O29  1  0.422  0.150  0.444  1.0
  O  O30  1  0.834  0.836  0.888  1.0
  O  O31  1  0.638  0.383  0.902  1.0
  O  O32  1  0.972  0.267  0.966  1.0
  O  O33  1  0.383  0.237  0.111  1.0
  O  O34  1  0.929  0.846  0.116  1.0
  O  O35  1  0.624  0.996  0.602  1.0
  O  O36  1  0.007  0.850  0.644  1.0
  O  O37  1  0.767  0.146  0.219  1.0
  O  O38  1  0.265  0.525  0.080  1.0
  O  O39  1  0.390  0.852  0.356  1.0
  O  O40  1  0.707  0.727  0.481  1.0
  O  O41  1  0.773  0.375  0.094  1.0
  O  O42  1  0.511  0.155  0.778  1.0
  O  O43  1  0.991  0.578  0.235  1.0
  O  O44  1  0.526  0.318  0.624  1.0
[/CIF]
.
The crystal structure described by Si2Sb15O28 crystallizes in the triclinic P1 space group. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one O(11), one O(22), one O(3), and one O(4) atom. In the second Si site, Si(2) is bonded to one O(15), one O(16), one O(25), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Sb(1)O5 square pyramid and  a cornercorner with one Sb(11)O5 square pyramid. There are fifteen inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to one O(21), one O(25), one O(27), one O(5), and one O(6) atom to form SbO5 square pyramids that share  a cornercorner with one Si(2)O4 tetrahedra. In the second Sb site, Sb(2) is bonded in a 4-coordinate geometry to one O(1), one O(14), one O(15), and one O(3) atom. In the third Sb site, Sb(3) is bonded in a distorted T-shaped geometry to one O(2), one O(23), and one O(24) atom. In the fourth Sb site, Sb(4) is bonded in a distorted T-shaped geometry to one O(2), one O(20), and one O(24) atom. In the fifth Sb site, Sb(5) is bonded in a distorted T-shaped geometry to one O(17), one O(22), and one O(6) atom. In the sixth Sb site, Sb(6) is bonded in a 3-coordinate geometry to one O(13), one O(19), and one O(28) atom. In the seventh Sb site, Sb(7) is bonded in a distorted rectangular see-saw-like geometry to one O(10), one O(11), one O(12), and one O(16) atom. In the eighth Sb site, Sb(8) is bonded in a rectangular see-saw-like geometry to one O(10), one O(14), one O(18), and one O(4) atom. In the ninth Sb site, Sb(9) is bonded in a distorted T-shaped geometry to one O(10), one O(26), and one O(9) atom. In the tenth Sb site, Sb(10) is bonded in a 4-coordinate geometry to one O(18), one O(25), one O(27), and one O(3) atom. In the eleventh Sb site, Sb(11) is bonded to one O(1), one O(12), one O(15), one O(26), and one O(28) atom to form distorted SbO5 square pyramids that share  a cornercorner with one Si(2)O4 tetrahedra. In the twelfth Sb site, Sb(12) is bonded in a distorted trigonal non-coplanar geometry to one O(17), one O(21), and one O(9) atom. In the thirteenth Sb site, Sb(13) is bonded in a distorted T-shaped geometry to one O(5), one O(7), and one O(8) atom. In the fourteenth Sb site, Sb(14) is bonded in a distorted trigonal non-coplanar geometry to one O(19), one O(20), and one O(8) atom. In the fifteenth Sb site, Sb(15) is bonded in a distorted trigonal non-coplanar geometry to one O(13), one O(23), and one O(7) atom. There are twenty-eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Sb(11) and one Sb(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Sb(3) and one Sb(4) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Si(1), one Sb(10), and one Sb(2) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(1) and one Sb(8) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Sb(1) and one Sb(13) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Sb(1) and one Sb(5) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Sb(13) and one Sb(15) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Sb(13) and one Sb(14) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Si(2), one Sb(12), and one Sb(9) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Sb(7), one Sb(8), and one Sb(9) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one Si(1) and one Sb(7) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one Sb(11) and one Sb(7) atom. In the thirteenth O site, O(13) is bonded in a bent 120 degrees geometry to one Sb(15) and one Sb(6) atom. In the fourteenth O site, O(14) is bonded in a bent 120 degrees geometry to one Sb(2) and one Sb(8) atom. In the fifteenth O site, O(15) is bonded in a 3-coordinate geometry to one Si(2), one Sb(11), and one Sb(2) atom. In the sixteenth O site, O(16) is bonded in a bent 150 degrees geometry to one Si(2) and one Sb(7) atom. In the seventeenth O site, O(17) is bonded in a bent 150 degrees geometry to one Sb(12) and one Sb(5) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Sb(10) and one Sb(8) atom. In the nineteenth O site, O(19) is bonded in a bent 150 degrees geometry to one Sb(14) and one Sb(6) atom. In the twentieth O site, O(20) is bonded in a bent 150 degrees geometry to one Sb(14) and one Sb(4) atom. In the twenty-first O site, O(21) is bonded in a bent 120 degrees geometry to one Sb(1) and one Sb(12) atom. In the twenty-second O site, O(22) is bonded in a linear geometry to one Si(1) and one Sb(5) atom. In the twenty-third O site, O(23) is bonded in a bent 150 degrees geometry to one Sb(15) and one Sb(3) atom. In the twenty-fourth O site, O(24) is bonded in a bent 150 degrees geometry to one Sb(3) and one Sb(4) atom. In the twenty-fifth O site, O(25) is bonded in a 1-coordinate geometry to one Si(2), one Sb(1), and one Sb(10) atom. In the twenty-sixth O site, O(26) is bonded in a bent 150 degrees geometry to one Sb(11) and one Sb(9) atom. In the twenty-seventh O site, O(27) is bonded in a water-like geometry to one Sb(1) and one Sb(10) atom. In the twenty-eighth O site, O(28) is bonded in a bent 120 degrees geometry to one Sb(11) and one Sb(6) atom. is represented by the CIF file [CIF]
data_Si2Sb15O28
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.027
_cell_length_b   9.403
_cell_length_c   14.279
_cell_angle_alpha   90.374
_cell_angle_beta   102.118
_cell_angle_gamma   97.003
_symmetry_Int_Tables_number   1
_cell_volume   915.161
_cell_formula_units_Z   1
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
  Si  Si0  1  0.147  0.616  0.996  1.0
  Si  Si1  1  0.764  0.296  0.992  1.0
  Sb  Sb2  1  0.897  0.358  0.250  1.0
  Sb  Sb3  1  0.664  0.651  0.894  1.0
  Sb  Sb4  1  0.408  0.680  0.434  1.0
  Sb  Sb5  1  0.965  0.677  0.560  1.0
  Sb  Sb6  1  0.377  0.411  0.190  1.0
  Sb  Sb7  1  0.394  0.106  0.577  1.0
  Sb  Sb8  1  0.141  0.328  0.873  1.0
  Sb  Sb9  1  0.036  0.938  1.000  1.0
  Sb  Sb10  1  0.453  0.005  0.869  1.0
  Sb  Sb11  1  0.800  0.653  0.131  1.0
  Sb  Sb12  1  0.642  0.351  0.759  1.0
  Sb  Sb13  1  0.535  0.073  0.125  1.0
  Sb  Sb14  1  0.838  0.105  0.419  1.0
  Sb  Sb15  1  0.904  0.032  0.666  1.0
  Sb  Sb16  1  0.267  0.031  0.330  1.0
  O  O17  1  0.662  0.563  0.765  1.0
  O  O18  1  0.223  0.736  0.515  1.0
  O  O19  1  0.908  0.600  0.003  1.0
  O  O20  1  0.227  0.788  0.004  1.0
  O  O21  1  0.959  0.304  0.387  1.0
  O  O22  1  0.145  0.309  0.226  1.0
  O  O23  1  0.038  0.988  0.388  1.0
  O  O24  1  0.979  0.139  0.556  1.0
  O  O25  1  0.635  0.130  0.994  1.0
  O  O26  1  0.215  0.058  0.896  1.0
  O  O27  1  0.146  0.545  0.892  1.0
  O  O28  1  0.911  0.323  0.762  1.0
  O  O29  1  0.422  0.150  0.444  1.0
  O  O30  1  0.834  0.836  0.888  1.0
  O  O31  1  0.638  0.383  0.902  1.0
  O  O32  1  0.972  0.267  0.966  1.0
  O  O33  1  0.383  0.237  0.111  1.0
  O  O34  1  0.929  0.846  0.116  1.0
  O  O35  1  0.624  0.996  0.602  1.0
  O  O36  1  0.007  0.850  0.644  1.0
  O  O37  1  0.767  0.146  0.219  1.0
  O  O38  1  0.265  0.525  0.080  1.0
  O  O39  1  0.390  0.852  0.356  1.0
  O  O40  1  0.707  0.727  0.481  1.0
  O  O41  1  0.773  0.375  0.094  1.0
  O  O42  1  0.511  0.155  0.778  1.0
  O  O43  1  0.991  0.578  0.235  1.0
  O  O44  1  0.526  0.318  0.624  1.0
[/CIF]
.