The material described by Cr20Al3Si9 crystallizes in the orthorhombic C222 space group. There are five inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a 7-coordinate geometry to one Cr(2), one Al(2), one Si(1), one Si(3), and three equivalent Si(4) atoms. In the second Cr site, Cr(2) is bonded in a 7-coordinate geometry to one Cr(1), one Al(1), one Al(3), one Si(2), and three equivalent Si(4) atoms. In the third Cr site, Cr(3) is bonded in a 7-coordinate geometry to one Cr(3), one Al(1), one Al(3), one Si(4), and three equivalent Si(2) atoms. In the fourth Cr site, Cr(4) is bonded in a 7-coordinate geometry to one Cr(4), one Al(2), one Si(1), one Si(4), and three equivalent Si(3) atoms. In the fifth Cr site, Cr(5) is bonded in a 6-coordinate geometry to two equivalent Cr(5), one Si(2), one Si(3), and two equivalent Si(4) atoms. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded in a distorted q6 geometry to four equivalent Cr(2), four equivalent Cr(3), and two equivalent Al(3) atoms. In the second Al site, Al(2) is bonded in a 10-coordinate geometry to four equivalent Cr(1), four equivalent Cr(4), and two equivalent Si(1) atoms. In the third Al site, Al(3) is bonded in a distorted q6 geometry to four equivalent Cr(2), four equivalent Cr(3), and two equivalent Al(1) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a distorted q6 geometry to four equivalent Cr(1), four equivalent Cr(4), and two equivalent Al(2) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Cr(2), two equivalent Cr(5), and six equivalent Cr(3) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to two equivalent Cr(1), two equivalent Cr(5), and six equivalent Cr(4) atoms. In the fourth Si site, Si(4) is bonded in a 10-coordinate geometry to one Cr(3), one Cr(4), two equivalent Cr(5), three equivalent Cr(1), and three equivalent Cr(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Al3Cr20Si9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.629
_cell_length_b   6.865
_cell_length_c   12.959
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   109.706
_symmetry_Int_Tables_number   1
_cell_volume   387.702
_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
  Al  Al0  1  0.250  0.000  0.000  1.0
  Al  Al1  1  0.750  0.000  0.500  1.0
  Al  Al2  1  0.750  0.000  0.000  1.0
  Cr  Cr3  1  0.929  0.846  0.346  1.0
  Cr  Cr4  1  0.420  0.841  0.843  1.0
  Cr  Cr5  1  0.579  0.159  0.157  1.0
  Cr  Cr6  1  0.083  0.154  0.654  1.0
  Cr  Cr7  1  0.159  0.318  0.079  1.0
  Cr  Cr8  1  0.650  0.312  0.577  1.0
  Cr  Cr9  1  0.339  0.688  0.423  1.0
  Cr  Cr10  1  0.841  0.682  0.921  1.0
  Cr  Cr11  1  0.341  0.682  0.079  1.0
  Cr  Cr12  1  0.850  0.688  0.577  1.0
  Cr  Cr13  1  0.161  0.312  0.423  1.0
  Cr  Cr14  1  0.659  0.318  0.921  1.0
  Cr  Cr15  1  0.571  0.154  0.346  1.0
  Cr  Cr16  1  0.080  0.159  0.843  1.0
  Cr  Cr17  1  0.921  0.841  0.157  1.0
  Cr  Cr18  1  0.417  0.846  0.654  1.0
  Cr  Cr19  1  0.497  0.500  0.251  1.0
  Cr  Cr20  1  0.997  0.500  0.749  1.0
  Cr  Cr21  1  0.003  0.500  0.251  1.0
  Cr  Cr22  1  0.503  0.500  0.749  1.0
  Si  Si23  1  0.250  0.000  0.500  1.0
  Si  Si24  1  0.750  0.500  0.085  1.0
  Si  Si25  1  0.250  0.500  0.584  1.0
  Si  Si26  1  0.750  0.500  0.416  1.0
  Si  Si27  1  0.250  0.500  0.915  1.0
  Si  Si28  1  0.420  0.835  0.250  1.0
  Si  Si29  1  0.915  0.835  0.750  1.0
  Si  Si30  1  0.080  0.165  0.250  1.0
  Si  Si31  1  0.585  0.165  0.750  1.0
[/CIF]
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The material described by Cr20Al3Si9 crystallizes in the orthorhombic C222 space group. There are five inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a 7-coordinate geometry to one Cr(2), one Al(2), one Si(1), one Si(3), and three equivalent Si(4) atoms. In the second Cr site, Cr(2) is bonded in a 7-coordinate geometry to one Cr(1), one Al(1), one Al(3), one Si(2), and three equivalent Si(4) atoms. In the third Cr site, Cr(3) is bonded in a 7-coordinate geometry to one Cr(3), one Al(1), one Al(3), one Si(4), and three equivalent Si(2) atoms. In the fourth Cr site, Cr(4) is bonded in a 7-coordinate geometry to one Cr(4), one Al(2), one Si(1), one Si(4), and three equivalent Si(3) atoms. In the fifth Cr site, Cr(5) is bonded in a 6-coordinate geometry to two equivalent Cr(5), one Si(2), one Si(3), and two equivalent Si(4) atoms. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded in a distorted q6 geometry to four equivalent Cr(2), four equivalent Cr(3), and two equivalent Al(3) atoms. In the second Al site, Al(2) is bonded in a 10-coordinate geometry to four equivalent Cr(1), four equivalent Cr(4), and two equivalent Si(1) atoms. In the third Al site, Al(3) is bonded in a distorted q6 geometry to four equivalent Cr(2), four equivalent Cr(3), and two equivalent Al(1) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a distorted q6 geometry to four equivalent Cr(1), four equivalent Cr(4), and two equivalent Al(2) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Cr(2), two equivalent Cr(5), and six equivalent Cr(3) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to two equivalent Cr(1), two equivalent Cr(5), and six equivalent Cr(4) atoms. In the fourth Si site, Si(4) is bonded in a 10-coordinate geometry to one Cr(3), one Cr(4), two equivalent Cr(5), three equivalent Cr(1), and three equivalent Cr(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Al3Cr20Si9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.629
_cell_length_b   6.865
_cell_length_c   12.959
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   109.706
_symmetry_Int_Tables_number   1
_cell_volume   387.702
_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
  Al  Al0  1  0.250  0.000  0.000  1.0
  Al  Al1  1  0.750  0.000  0.500  1.0
  Al  Al2  1  0.750  0.000  0.000  1.0
  Cr  Cr3  1  0.929  0.846  0.346  1.0
  Cr  Cr4  1  0.420  0.841  0.843  1.0
  Cr  Cr5  1  0.579  0.159  0.157  1.0
  Cr  Cr6  1  0.083  0.154  0.654  1.0
  Cr  Cr7  1  0.159  0.318  0.079  1.0
  Cr  Cr8  1  0.650  0.312  0.577  1.0
  Cr  Cr9  1  0.339  0.688  0.423  1.0
  Cr  Cr10  1  0.841  0.682  0.921  1.0
  Cr  Cr11  1  0.341  0.682  0.079  1.0
  Cr  Cr12  1  0.850  0.688  0.577  1.0
  Cr  Cr13  1  0.161  0.312  0.423  1.0
  Cr  Cr14  1  0.659  0.318  0.921  1.0
  Cr  Cr15  1  0.571  0.154  0.346  1.0
  Cr  Cr16  1  0.080  0.159  0.843  1.0
  Cr  Cr17  1  0.921  0.841  0.157  1.0
  Cr  Cr18  1  0.417  0.846  0.654  1.0
  Cr  Cr19  1  0.497  0.500  0.251  1.0
  Cr  Cr20  1  0.997  0.500  0.749  1.0
  Cr  Cr21  1  0.003  0.500  0.251  1.0
  Cr  Cr22  1  0.503  0.500  0.749  1.0
  Si  Si23  1  0.250  0.000  0.500  1.0
  Si  Si24  1  0.750  0.500  0.085  1.0
  Si  Si25  1  0.250  0.500  0.584  1.0
  Si  Si26  1  0.750  0.500  0.416  1.0
  Si  Si27  1  0.250  0.500  0.915  1.0
  Si  Si28  1  0.420  0.835  0.250  1.0
  Si  Si29  1  0.915  0.835  0.750  1.0
  Si  Si30  1  0.080  0.165  0.250  1.0
  Si  Si31  1  0.585  0.165  0.750  1.0
[/CIF]
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