The crystal structure described by Ca4SiN4 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one N(2), one N(3), one N(4), and two equivalent N(1) atoms. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one N(3), two equivalent N(1), and two equivalent N(2) atoms. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one N(1), one N(2), one N(3), and two equivalent N(4) atoms. In the fourth Ca site, Ca(4) is bonded to one N(2), two equivalent N(3), and two equivalent N(4) atoms to form distorted CaN5 trigonal bipyramids that share  a cornercorner with one Si(1)N4 tetrahedra, edges with two equivalent Si(1)N4 tetrahedra, and edges with two equivalent Ca(4)N5 trigonal bipyramids. Si(1) is bonded to one N(1), one N(2), one N(3), and one N(4) atom to form SiN4 tetrahedra that share  a cornercorner with one Ca(4)N5 trigonal bipyramid and edges with two equivalent Ca(4)N5 trigonal bipyramids. There are four inequivalent N sites. In the first N site, N(4) is bonded to one Ca(1), two equivalent Ca(3), two equivalent Ca(4), and one Si(1) atom to form a mixture of distorted corner, face, and edge-sharing NCa5Si octahedra. The corner-sharing octahedral tilt angles range from 16-65°. In the second N site, N(1) is bonded to one Ca(3), two equivalent Ca(1), two equivalent Ca(2), and one Si(1) atom to form a mixture of distorted corner, face, and edge-sharing NCa5Si octahedra. The corner-sharing octahedral tilt angles range from 16-57°. In the third N site, N(2) is bonded in a 6-coordinate geometry to one Ca(1), one Ca(3), one Ca(4), two equivalent Ca(2), and one Si(1) atom. In the fourth N site, N(3) is bonded in a 6-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), two equivalent Ca(4), and one Si(1) atom. is represented by the CIF card [CIF]
data_Ca4SiN4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.971
_cell_length_b   9.163
_cell_length_c   10.977
_cell_angle_alpha   63.683
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   538.363
_cell_formula_units_Z   4
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  0.922  0.351  0.654  1.0
  Ca  Ca1  1  0.422  0.649  0.846  1.0
  Ca  Ca2  1  0.078  0.649  0.346  1.0
  Ca  Ca3  1  0.578  0.351  0.154  1.0
  Ca  Ca4  1  0.919  0.454  0.879  1.0
  Ca  Ca5  1  0.419  0.546  0.621  1.0
  Ca  Ca6  1  0.081  0.546  0.121  1.0
  Ca  Ca7  1  0.581  0.454  0.379  1.0
  Ca  Ca8  1  0.849  0.855  0.769  1.0
  Ca  Ca9  1  0.349  0.145  0.731  1.0
  Ca  Ca10  1  0.151  0.145  0.231  1.0
  Ca  Ca11  1  0.651  0.855  0.269  1.0
  Ca  Ca12  1  0.256  0.919  0.544  1.0
  Ca  Ca13  1  0.756  0.081  0.956  1.0
  Ca  Ca14  1  0.744  0.081  0.456  1.0
  Ca  Ca15  1  0.244  0.919  0.044  1.0
  Si  Si16  1  0.853  0.733  0.548  1.0
  Si  Si17  1  0.353  0.267  0.952  1.0
  Si  Si18  1  0.147  0.267  0.452  1.0
  Si  Si19  1  0.647  0.733  0.048  1.0
  N  N20  1  0.746  0.595  0.988  1.0
  N  N21  1  0.246  0.405  0.512  1.0
  N  N22  1  0.254  0.405  0.012  1.0
  N  N23  1  0.754  0.595  0.488  1.0
  N  N24  1  0.068  0.662  0.674  1.0
  N  N25  1  0.568  0.338  0.826  1.0
  N  N26  1  0.932  0.338  0.326  1.0
  N  N27  1  0.432  0.662  0.174  1.0
  N  N28  1  0.621  0.800  0.612  1.0
  N  N29  1  0.121  0.200  0.888  1.0
  N  N30  1  0.379  0.200  0.388  1.0
  N  N31  1  0.879  0.800  0.112  1.0
  N  N32  1  0.531  0.898  0.895  1.0
  N  N33  1  0.031  0.102  0.605  1.0
  N  N34  1  0.469  0.102  0.105  1.0
  N  N35  1  0.969  0.898  0.395  1.0
[/CIF]
.
The crystal structure described by Ca4SiN4 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one N(2), one N(3), one N(4), and two equivalent N(1) atoms. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one N(3), two equivalent N(1), and two equivalent N(2) atoms. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one N(1), one N(2), one N(3), and two equivalent N(4) atoms. In the fourth Ca site, Ca(4) is bonded to one N(2), two equivalent N(3), and two equivalent N(4) atoms to form distorted CaN5 trigonal bipyramids that share  a cornercorner with one Si(1)N4 tetrahedra, edges with two equivalent Si(1)N4 tetrahedra, and edges with two equivalent Ca(4)N5 trigonal bipyramids. Si(1) is bonded to one N(1), one N(2), one N(3), and one N(4) atom to form SiN4 tetrahedra that share  a cornercorner with one Ca(4)N5 trigonal bipyramid and edges with two equivalent Ca(4)N5 trigonal bipyramids. There are four inequivalent N sites. In the first N site, N(4) is bonded to one Ca(1), two equivalent Ca(3), two equivalent Ca(4), and one Si(1) atom to form a mixture of distorted corner, face, and edge-sharing NCa5Si octahedra. The corner-sharing octahedral tilt angles range from 16-65°. In the second N site, N(1) is bonded to one Ca(3), two equivalent Ca(1), two equivalent Ca(2), and one Si(1) atom to form a mixture of distorted corner, face, and edge-sharing NCa5Si octahedra. The corner-sharing octahedral tilt angles range from 16-57°. In the third N site, N(2) is bonded in a 6-coordinate geometry to one Ca(1), one Ca(3), one Ca(4), two equivalent Ca(2), and one Si(1) atom. In the fourth N site, N(3) is bonded in a 6-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), two equivalent Ca(4), and one Si(1) atom. is represented by the CIF card [CIF]
data_Ca4SiN4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.971
_cell_length_b   9.163
_cell_length_c   10.977
_cell_angle_alpha   63.683
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   538.363
_cell_formula_units_Z   4
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  0.922  0.351  0.654  1.0
  Ca  Ca1  1  0.422  0.649  0.846  1.0
  Ca  Ca2  1  0.078  0.649  0.346  1.0
  Ca  Ca3  1  0.578  0.351  0.154  1.0
  Ca  Ca4  1  0.919  0.454  0.879  1.0
  Ca  Ca5  1  0.419  0.546  0.621  1.0
  Ca  Ca6  1  0.081  0.546  0.121  1.0
  Ca  Ca7  1  0.581  0.454  0.379  1.0
  Ca  Ca8  1  0.849  0.855  0.769  1.0
  Ca  Ca9  1  0.349  0.145  0.731  1.0
  Ca  Ca10  1  0.151  0.145  0.231  1.0
  Ca  Ca11  1  0.651  0.855  0.269  1.0
  Ca  Ca12  1  0.256  0.919  0.544  1.0
  Ca  Ca13  1  0.756  0.081  0.956  1.0
  Ca  Ca14  1  0.744  0.081  0.456  1.0
  Ca  Ca15  1  0.244  0.919  0.044  1.0
  Si  Si16  1  0.853  0.733  0.548  1.0
  Si  Si17  1  0.353  0.267  0.952  1.0
  Si  Si18  1  0.147  0.267  0.452  1.0
  Si  Si19  1  0.647  0.733  0.048  1.0
  N  N20  1  0.746  0.595  0.988  1.0
  N  N21  1  0.246  0.405  0.512  1.0
  N  N22  1  0.254  0.405  0.012  1.0
  N  N23  1  0.754  0.595  0.488  1.0
  N  N24  1  0.068  0.662  0.674  1.0
  N  N25  1  0.568  0.338  0.826  1.0
  N  N26  1  0.932  0.338  0.326  1.0
  N  N27  1  0.432  0.662  0.174  1.0
  N  N28  1  0.621  0.800  0.612  1.0
  N  N29  1  0.121  0.200  0.888  1.0
  N  N30  1  0.379  0.200  0.388  1.0
  N  N31  1  0.879  0.800  0.112  1.0
  N  N32  1  0.531  0.898  0.895  1.0
  N  N33  1  0.031  0.102  0.605  1.0
  N  N34  1  0.469  0.102  0.105  1.0
  N  N35  1  0.969  0.898  0.395  1.0
[/CIF]
.