The material structure described by K2Al2B2O7 crystallizes in the monoclinic C2 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to one O(10), one O(11), one O(2), one O(4), one O(5), one O(7), one O(9), and two equivalent O(3) atoms. In the second K site, K(2) is bonded in a 4-coordinate geometry to two equivalent O(4) and two equivalent O(8) atoms. In the third K site, K(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), two equivalent O(6), and two equivalent O(8) atoms. In the fourth K site, K(4) is bonded in a 2-coordinate geometry to one O(5) and one O(7) atom. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(11), one O(5), one O(6), and one O(7) atom to form corner-sharing AlO4 tetrahedra. In the second Al site, Al(2) is bonded to one O(1), one O(10), one O(8), and one O(9) atom to form corner-sharing AlO4 tetrahedra. In the third Al site, Al(3) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing AlO4 tetrahedra. There are three inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(2), one O(5), and one O(8) atom. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(3), one O(6), and one O(9) atom. In the third B site, B(3) is bonded in a trigonal planar geometry to one O(10), one O(4), and one O(7) atom. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one K(3), one Al(2), and one Al(3) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one K(1), one Al(3), and one B(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to two equivalent K(1), one Al(3), and one B(2) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one K(1), one K(2), one K(3), one Al(3), and one B(3) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one K(1), one K(4), one Al(1), and one B(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one K(3), one Al(1), and one B(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one K(1), one K(4), one Al(1), and one B(3) atom. In the eighth O site, O(8) is bonded in a 2-coordinate geometry to one K(2), one K(3), one Al(2), and one B(1) atom. In the ninth O site, O(9) is bonded in a 2-coordinate geometry to one K(1), one Al(2), and one B(2) atom. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one K(1), one Al(2), and one B(3) atom. In the eleventh O site, O(11) is bonded in a distorted linear geometry to two equivalent K(1) and two equivalent Al(1) atoms. is represented by the CIF file [CIF]
data_K2Al2B2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.667
_cell_length_b   8.667
_cell_length_c   8.580
_cell_angle_alpha   89.921
_cell_angle_beta   89.921
_cell_angle_gamma   59.992
_symmetry_Int_Tables_number   1
_cell_volume   558.158
_cell_formula_units_Z   3
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  0.001  0.641  0.500  1.0
  K  K1  1  0.359  0.999  0.500  1.0
  K  K2  1  0.639  0.361  0.500  1.0
  K  K3  1  0.692  0.308  0.000  1.0
  K  K4  1  0.000  0.690  0.998  1.0
  K  K5  1  0.310  1.000  0.002  1.0
  Al  Al6  1  0.006  0.994  0.299  1.0
  Al  Al7  1  0.006  0.994  0.701  1.0
  Al  Al8  1  0.333  0.333  0.186  1.0
  Al  Al9  1  0.667  0.667  0.814  1.0
  Al  Al10  1  0.333  0.333  0.783  1.0
  Al  Al11  1  0.667  0.667  0.217  1.0
  B  B12  1  0.335  0.664  0.747  1.0
  B  B13  1  0.001  0.332  0.742  1.0
  B  B14  1  0.666  0.001  0.743  1.0
  B  B15  1  0.999  0.334  0.257  1.0
  B  B16  1  0.668  0.999  0.258  1.0
  B  B17  1  0.336  0.665  0.253  1.0
  O  O18  1  0.334  0.333  0.984  1.0
  O  O19  1  0.667  0.666  0.016  1.0
  O  O20  1  0.272  0.549  0.712  1.0
  O  O21  1  0.180  0.272  0.711  1.0
  O  O22  1  0.548  0.180  0.711  1.0
  O  O23  1  0.820  0.452  0.289  1.0
  O  O24  1  0.728  0.820  0.289  1.0
  O  O25  1  0.451  0.728  0.288  1.0
  O  O26  1  0.215  0.839  0.785  1.0
  O  O27  1  0.944  0.212  0.769  1.0
  O  O28  1  0.843  0.944  0.773  1.0
  O  O29  1  0.056  0.157  0.227  1.0
  O  O30  1  0.788  0.056  0.231  1.0
  O  O31  1  0.161  0.785  0.215  1.0
  O  O32  1  0.516  0.602  0.744  1.0
  O  O33  1  0.883  0.513  0.745  1.0
  O  O34  1  0.603  0.883  0.745  1.0
  O  O35  1  0.117  0.397  0.255  1.0
  O  O36  1  0.487  0.117  0.255  1.0
  O  O37  1  0.398  0.484  0.256  1.0
  O  O38  1  0.019  0.981  0.500  1.0
[/CIF]
.
The material structure described by K2Al2B2O7 crystallizes in the monoclinic C2 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to one O(10), one O(11), one O(2), one O(4), one O(5), one O(7), one O(9), and two equivalent O(3) atoms. In the second K site, K(2) is bonded in a 4-coordinate geometry to two equivalent O(4) and two equivalent O(8) atoms. In the third K site, K(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), two equivalent O(6), and two equivalent O(8) atoms. In the fourth K site, K(4) is bonded in a 2-coordinate geometry to one O(5) and one O(7) atom. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(11), one O(5), one O(6), and one O(7) atom to form corner-sharing AlO4 tetrahedra. In the second Al site, Al(2) is bonded to one O(1), one O(10), one O(8), and one O(9) atom to form corner-sharing AlO4 tetrahedra. In the third Al site, Al(3) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing AlO4 tetrahedra. There are three inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(2), one O(5), and one O(8) atom. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(3), one O(6), and one O(9) atom. In the third B site, B(3) is bonded in a trigonal planar geometry to one O(10), one O(4), and one O(7) atom. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one K(3), one Al(2), and one Al(3) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one K(1), one Al(3), and one B(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to two equivalent K(1), one Al(3), and one B(2) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one K(1), one K(2), one K(3), one Al(3), and one B(3) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one K(1), one K(4), one Al(1), and one B(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one K(3), one Al(1), and one B(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one K(1), one K(4), one Al(1), and one B(3) atom. In the eighth O site, O(8) is bonded in a 2-coordinate geometry to one K(2), one K(3), one Al(2), and one B(1) atom. In the ninth O site, O(9) is bonded in a 2-coordinate geometry to one K(1), one Al(2), and one B(2) atom. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one K(1), one Al(2), and one B(3) atom. In the eleventh O site, O(11) is bonded in a distorted linear geometry to two equivalent K(1) and two equivalent Al(1) atoms. is represented by the CIF file [CIF]
data_K2Al2B2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.667
_cell_length_b   8.667
_cell_length_c   8.580
_cell_angle_alpha   89.921
_cell_angle_beta   89.921
_cell_angle_gamma   59.992
_symmetry_Int_Tables_number   1
_cell_volume   558.158
_cell_formula_units_Z   3
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  0.001  0.641  0.500  1.0
  K  K1  1  0.359  0.999  0.500  1.0
  K  K2  1  0.639  0.361  0.500  1.0
  K  K3  1  0.692  0.308  0.000  1.0
  K  K4  1  0.000  0.690  0.998  1.0
  K  K5  1  0.310  1.000  0.002  1.0
  Al  Al6  1  0.006  0.994  0.299  1.0
  Al  Al7  1  0.006  0.994  0.701  1.0
  Al  Al8  1  0.333  0.333  0.186  1.0
  Al  Al9  1  0.667  0.667  0.814  1.0
  Al  Al10  1  0.333  0.333  0.783  1.0
  Al  Al11  1  0.667  0.667  0.217  1.0
  B  B12  1  0.335  0.664  0.747  1.0
  B  B13  1  0.001  0.332  0.742  1.0
  B  B14  1  0.666  0.001  0.743  1.0
  B  B15  1  0.999  0.334  0.257  1.0
  B  B16  1  0.668  0.999  0.258  1.0
  B  B17  1  0.336  0.665  0.253  1.0
  O  O18  1  0.334  0.333  0.984  1.0
  O  O19  1  0.667  0.666  0.016  1.0
  O  O20  1  0.272  0.549  0.712  1.0
  O  O21  1  0.180  0.272  0.711  1.0
  O  O22  1  0.548  0.180  0.711  1.0
  O  O23  1  0.820  0.452  0.289  1.0
  O  O24  1  0.728  0.820  0.289  1.0
  O  O25  1  0.451  0.728  0.288  1.0
  O  O26  1  0.215  0.839  0.785  1.0
  O  O27  1  0.944  0.212  0.769  1.0
  O  O28  1  0.843  0.944  0.773  1.0
  O  O29  1  0.056  0.157  0.227  1.0
  O  O30  1  0.788  0.056  0.231  1.0
  O  O31  1  0.161  0.785  0.215  1.0
  O  O32  1  0.516  0.602  0.744  1.0
  O  O33  1  0.883  0.513  0.745  1.0
  O  O34  1  0.603  0.883  0.745  1.0
  O  O35  1  0.117  0.397  0.255  1.0
  O  O36  1  0.487  0.117  0.255  1.0
  O  O37  1  0.398  0.484  0.256  1.0
  O  O38  1  0.019  0.981  0.500  1.0
[/CIF]
.