The material described by SrCa2(FeAs)6 crystallizes in the monoclinic C2/m space group. Sr(1) is bonded in a 16-coordinate geometry to four equivalent Fe(1), four equivalent Fe(2), two equivalent As(1), two equivalent As(3), and four equivalent As(2) atoms. Ca(1) is bonded in a 16-coordinate geometry to two equivalent Fe(2), six equivalent Fe(1), two equivalent As(2), three equivalent As(1), and three equivalent As(3) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Sr(1), three equivalent Ca(1), one As(1), one As(2), and two equivalent As(3) atoms to form distorted FeSrCa3As4 tetrahedra that share corners with four equivalent Fe(2)Sr2Ca2As4 tetrahedra, corners with eight equivalent Fe(1)SrCa3As4 tetrahedra, edges with three equivalent Fe(2)Sr2Ca2As4 tetrahedra, edges with three equivalent Fe(1)SrCa3As4 tetrahedra,  a faceface with one Fe(2)Sr2Ca2As4 tetrahedra, and faces with three equivalent Fe(1)SrCa3As4 tetrahedra. In the second Fe site, Fe(2) is bonded to two equivalent Sr(1), two equivalent Ca(1), two equivalent As(1), and two equivalent As(2) atoms to form distorted FeSr2Ca2As4 tetrahedra that share corners with four equivalent Fe(2)Sr2Ca2As4 tetrahedra, corners with eight equivalent Fe(1)SrCa3As4 tetrahedra, edges with six equivalent Fe(1)SrCa3As4 tetrahedra, faces with two equivalent Fe(2)Sr2Ca2As4 tetrahedra, and faces with two equivalent Fe(1)SrCa3As4 tetrahedra. There are three inequivalent As sites. In the first As site, As(1) is bonded in a 4-coordinate geometry to one Sr(1), three equivalent Ca(1), two equivalent Fe(1), and two equivalent Fe(2) atoms. In the second As site, As(2) is bonded in a 4-coordinate geometry to two equivalent Sr(1), two equivalent Ca(1), two equivalent Fe(1), and two equivalent Fe(2) atoms. In the third As site, As(3) is bonded in a 4-coordinate geometry to one Sr(1), three equivalent Ca(1), and four equivalent Fe(1) atoms. is represented by the CIF file [CIF]
data_SrCa2(FeAs)6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.653
_cell_length_b   6.060
_cell_length_c   8.307
_cell_angle_alpha   75.125
_cell_angle_beta   70.107
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   257.441
_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
  Sr  Sr0  1  0.000  0.000  0.000  1.0
  Ca  Ca1  1  0.333  0.664  0.335  1.0
  Ca  Ca2  1  0.667  0.336  0.665  1.0
  Fe  Fe3  1  0.418  0.834  0.665  1.0
  Fe  Fe4  1  0.750  0.500  0.000  1.0
  Fe  Fe5  1  0.083  0.166  0.335  1.0
  Fe  Fe6  1  0.250  0.500  0.000  1.0
  Fe  Fe7  1  0.582  0.166  0.335  1.0
  Fe  Fe8  1  0.917  0.834  0.665  1.0
  As  As9  1  0.120  0.523  0.760  1.0
  As  As10  1  0.452  0.189  0.096  1.0
  As  As11  1  0.786  0.852  0.427  1.0
  As  As12  1  0.548  0.811  0.904  1.0
  As  As13  1  0.880  0.477  0.240  1.0
  As  As14  1  0.214  0.148  0.573  1.0
[/CIF]
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The material described by SrCa2(FeAs)6 crystallizes in the monoclinic C2/m space group. Sr(1) is bonded in a 16-coordinate geometry to four equivalent Fe(1), four equivalent Fe(2), two equivalent As(1), two equivalent As(3), and four equivalent As(2) atoms. Ca(1) is bonded in a 16-coordinate geometry to two equivalent Fe(2), six equivalent Fe(1), two equivalent As(2), three equivalent As(1), and three equivalent As(3) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Sr(1), three equivalent Ca(1), one As(1), one As(2), and two equivalent As(3) atoms to form distorted FeSrCa3As4 tetrahedra that share corners with four equivalent Fe(2)Sr2Ca2As4 tetrahedra, corners with eight equivalent Fe(1)SrCa3As4 tetrahedra, edges with three equivalent Fe(2)Sr2Ca2As4 tetrahedra, edges with three equivalent Fe(1)SrCa3As4 tetrahedra,  a faceface with one Fe(2)Sr2Ca2As4 tetrahedra, and faces with three equivalent Fe(1)SrCa3As4 tetrahedra. In the second Fe site, Fe(2) is bonded to two equivalent Sr(1), two equivalent Ca(1), two equivalent As(1), and two equivalent As(2) atoms to form distorted FeSr2Ca2As4 tetrahedra that share corners with four equivalent Fe(2)Sr2Ca2As4 tetrahedra, corners with eight equivalent Fe(1)SrCa3As4 tetrahedra, edges with six equivalent Fe(1)SrCa3As4 tetrahedra, faces with two equivalent Fe(2)Sr2Ca2As4 tetrahedra, and faces with two equivalent Fe(1)SrCa3As4 tetrahedra. There are three inequivalent As sites. In the first As site, As(1) is bonded in a 4-coordinate geometry to one Sr(1), three equivalent Ca(1), two equivalent Fe(1), and two equivalent Fe(2) atoms. In the second As site, As(2) is bonded in a 4-coordinate geometry to two equivalent Sr(1), two equivalent Ca(1), two equivalent Fe(1), and two equivalent Fe(2) atoms. In the third As site, As(3) is bonded in a 4-coordinate geometry to one Sr(1), three equivalent Ca(1), and four equivalent Fe(1) atoms. is represented by the CIF file [CIF]
data_SrCa2(FeAs)6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.653
_cell_length_b   6.060
_cell_length_c   8.307
_cell_angle_alpha   75.125
_cell_angle_beta   70.107
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   257.441
_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
  Sr  Sr0  1  0.000  0.000  0.000  1.0
  Ca  Ca1  1  0.333  0.664  0.335  1.0
  Ca  Ca2  1  0.667  0.336  0.665  1.0
  Fe  Fe3  1  0.418  0.834  0.665  1.0
  Fe  Fe4  1  0.750  0.500  0.000  1.0
  Fe  Fe5  1  0.083  0.166  0.335  1.0
  Fe  Fe6  1  0.250  0.500  0.000  1.0
  Fe  Fe7  1  0.582  0.166  0.335  1.0
  Fe  Fe8  1  0.917  0.834  0.665  1.0
  As  As9  1  0.120  0.523  0.760  1.0
  As  As10  1  0.452  0.189  0.096  1.0
  As  As11  1  0.786  0.852  0.427  1.0
  As  As12  1  0.548  0.811  0.904  1.0
  As  As13  1  0.880  0.477  0.240  1.0
  As  As14  1  0.214  0.148  0.573  1.0
[/CIF]
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