The structure described by Ca3Al2As4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form distorted CaAs6 octahedra that share corners with eight equivalent Al(1)As4 tetrahedra, edges with two equivalent Ca(1)As6 octahedra, and edges with two equivalent Al(1)As4 tetrahedra. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to three equivalent As(1) and three equivalent As(2) atoms. Al(1) is bonded to two equivalent As(1) and two equivalent As(2) atoms to form distorted AlAs4 tetrahedra that share corners with four equivalent Ca(1)As6 octahedra, corners with two equivalent Al(1)As4 tetrahedra,  an edgeedge with one Ca(1)As6 octahedra, and  an edgeedge with one Al(1)As4 tetrahedra. The corner-sharing octahedral tilt angles range from 21-64°. There are two inequivalent As sites. In the first As site, As(1) is bonded in a 6-coordinate geometry to one Ca(1), three equivalent Ca(2), and two equivalent Al(1) atoms. In the second As site, As(2) is bonded in a 7-coordinate geometry to two equivalent Ca(1), three equivalent Ca(2), and two equivalent Al(1) atoms. is represented by the CIF card [CIF]
data_Ca3(AlAs2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.890
_cell_length_b   7.890
_cell_length_c   8.284
_cell_angle_alpha   87.081
_cell_angle_beta   87.081
_cell_angle_gamma   62.133
_symmetry_Int_Tables_number   1
_cell_volume   455.081
_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
  Ca  Ca0  1  0.848  0.152  0.750  1.0
  Ca  Ca1  1  0.366  0.914  0.862  1.0
  Ca  Ca2  1  0.634  0.086  0.138  1.0
  Ca  Ca3  1  0.914  0.366  0.362  1.0
  Ca  Ca4  1  0.152  0.848  0.250  1.0
  Ca  Ca5  1  0.086  0.634  0.638  1.0
  Al  Al6  1  0.582  0.809  0.457  1.0
  Al  Al7  1  0.191  0.418  0.043  1.0
  Al  Al8  1  0.418  0.191  0.543  1.0
  Al  Al9  1  0.809  0.582  0.957  1.0
  As  As10  1  0.735  0.558  0.671  1.0
  As  As11  1  0.442  0.265  0.829  1.0
  As  As12  1  0.558  0.735  0.171  1.0
  As  As13  1  0.265  0.442  0.329  1.0
  As  As14  1  1.000  0.771  0.963  1.0
  As  As15  1  0.229  0.000  0.537  1.0
  As  As16  1  0.000  0.229  0.037  1.0
  As  As17  1  0.771  1.000  0.463  1.0
[/CIF]
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The structure described by Ca3Al2As4 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent As(1) and four equivalent As(2) atoms to form distorted CaAs6 octahedra that share corners with eight equivalent Al(1)As4 tetrahedra, edges with two equivalent Ca(1)As6 octahedra, and edges with two equivalent Al(1)As4 tetrahedra. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to three equivalent As(1) and three equivalent As(2) atoms. Al(1) is bonded to two equivalent As(1) and two equivalent As(2) atoms to form distorted AlAs4 tetrahedra that share corners with four equivalent Ca(1)As6 octahedra, corners with two equivalent Al(1)As4 tetrahedra,  an edgeedge with one Ca(1)As6 octahedra, and  an edgeedge with one Al(1)As4 tetrahedra. The corner-sharing octahedral tilt angles range from 21-64°. There are two inequivalent As sites. In the first As site, As(1) is bonded in a 6-coordinate geometry to one Ca(1), three equivalent Ca(2), and two equivalent Al(1) atoms. In the second As site, As(2) is bonded in a 7-coordinate geometry to two equivalent Ca(1), three equivalent Ca(2), and two equivalent Al(1) atoms. is represented by the CIF card [CIF]
data_Ca3(AlAs2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.890
_cell_length_b   7.890
_cell_length_c   8.284
_cell_angle_alpha   87.081
_cell_angle_beta   87.081
_cell_angle_gamma   62.133
_symmetry_Int_Tables_number   1
_cell_volume   455.081
_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
  Ca  Ca0  1  0.848  0.152  0.750  1.0
  Ca  Ca1  1  0.366  0.914  0.862  1.0
  Ca  Ca2  1  0.634  0.086  0.138  1.0
  Ca  Ca3  1  0.914  0.366  0.362  1.0
  Ca  Ca4  1  0.152  0.848  0.250  1.0
  Ca  Ca5  1  0.086  0.634  0.638  1.0
  Al  Al6  1  0.582  0.809  0.457  1.0
  Al  Al7  1  0.191  0.418  0.043  1.0
  Al  Al8  1  0.418  0.191  0.543  1.0
  Al  Al9  1  0.809  0.582  0.957  1.0
  As  As10  1  0.735  0.558  0.671  1.0
  As  As11  1  0.442  0.265  0.829  1.0
  As  As12  1  0.558  0.735  0.171  1.0
  As  As13  1  0.265  0.442  0.329  1.0
  As  As14  1  1.000  0.771  0.963  1.0
  As  As15  1  0.229  0.000  0.537  1.0
  As  As16  1  0.000  0.229  0.037  1.0
  As  As17  1  0.771  1.000  0.463  1.0
[/CIF]
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