The structure described by Ca2Si5N8 is Chalcostibite-like structured and crystallizes in the monoclinic Cc space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one N(1), one N(2), one N(4), one N(5), one N(8), and two equivalent N(7) atoms. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one N(1), one N(2), one N(3), one N(7), one N(8), and two equivalent N(4) atoms. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded to one N(3), one N(4), one N(5), and one N(6) atom to form corner-sharing SiN4 tetrahedra. In the second Si site, Si(2) is bonded to one N(1), one N(3), one N(5), and one N(8) atom to form corner-sharing SiN4 tetrahedra. In the third Si site, Si(3) is bonded to one N(1), one N(5), one N(6), and one N(7) atom to form corner-sharing SiN4 tetrahedra. In the fourth Si site, Si(4) is bonded to one N(1), one N(2), one N(3), and one N(6) atom to form corner-sharing SiN4 tetrahedra. In the fifth Si site, Si(5) is bonded to one N(2), one N(4), one N(7), and one N(8) atom to form corner-sharing SiN4 tetrahedra. There are eight inequivalent N sites. In the first N site, N(3) is bonded in a distorted trigonal pyramidal geometry to one Ca(2), one Si(1), one Si(2), and one Si(4) atom. In the second N site, N(4) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Ca(2), one Si(1), and one Si(5) atom. In the third N site, N(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Si(1), one Si(2), and one Si(3) atom. In the fourth N site, N(6) is bonded in a trigonal planar geometry to one Si(1), one Si(3), and one Si(4) atom. In the fifth N site, N(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), one Si(3), and one Si(5) atom. In the sixth N site, N(8) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Si(2), and one Si(5) atom. In the seventh N site, N(1) is bonded in a trigonal planar geometry to one Ca(1), one Ca(2), one Si(2), one Si(3), and one Si(4) atom. In the eighth N site, N(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Si(4), and one Si(5) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2Si5N8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.704
_cell_length_b   7.704
_cell_length_c   9.681
_cell_angle_alpha   69.562
_cell_angle_beta   69.562
_cell_angle_gamma   42.653
_symmetry_Int_Tables_number   1
_cell_volume   360.889
_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  0.357  0.864  0.301  1.0
  Ca  Ca1  1  0.864  0.357  0.801  1.0
  Ca  Ca2  1  0.764  0.236  0.498  1.0
  Ca  Ca3  1  0.236  0.764  0.998  1.0
  Si  Si4  1  0.858  0.853  0.374  1.0
  Si  Si5  1  0.853  0.858  0.874  1.0
  Si  Si6  1  0.571  0.154  0.132  1.0
  Si  Si7  1  0.154  0.571  0.632  1.0
  Si  Si8  1  0.251  0.258  0.437  1.0
  Si  Si9  1  0.258  0.251  0.937  1.0
  Si  Si10  1  0.966  0.546  0.182  1.0
  Si  Si11  1  0.546  0.966  0.682  1.0
  Si  Si12  1  0.864  0.251  0.147  1.0
  Si  Si13  1  0.251  0.864  0.647  1.0
  N  N14  1  0.279  0.313  0.084  1.0
  N  N15  1  0.313  0.279  0.584  1.0
  N  N16  1  0.789  0.474  0.227  1.0
  N  N17  1  0.474  0.789  0.727  1.0
  N  N18  1  0.848  0.819  0.565  1.0
  N  N19  1  0.819  0.848  0.065  1.0
  N  N20  1  0.978  0.983  0.282  1.0
  N  N21  1  0.983  0.978  0.782  1.0
  N  N22  1  0.551  0.056  0.324  1.0
  N  N23  1  0.056  0.551  0.824  1.0
  N  N24  1  0.037  0.553  0.330  1.0
  N  N25  1  0.553  0.037  0.830  1.0
  N  N26  1  0.138  0.120  0.504  1.0
  N  N27  1  0.120  0.138  0.004  1.0
  N  N28  1  0.346  0.627  0.571  1.0
  N  N29  1  0.627  0.346  0.071  1.0
[/CIF]
.
The structure described by Ca2Si5N8 is Chalcostibite-like structured and crystallizes in the monoclinic Cc space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one N(1), one N(2), one N(4), one N(5), one N(8), and two equivalent N(7) atoms. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one N(1), one N(2), one N(3), one N(7), one N(8), and two equivalent N(4) atoms. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded to one N(3), one N(4), one N(5), and one N(6) atom to form corner-sharing SiN4 tetrahedra. In the second Si site, Si(2) is bonded to one N(1), one N(3), one N(5), and one N(8) atom to form corner-sharing SiN4 tetrahedra. In the third Si site, Si(3) is bonded to one N(1), one N(5), one N(6), and one N(7) atom to form corner-sharing SiN4 tetrahedra. In the fourth Si site, Si(4) is bonded to one N(1), one N(2), one N(3), and one N(6) atom to form corner-sharing SiN4 tetrahedra. In the fifth Si site, Si(5) is bonded to one N(2), one N(4), one N(7), and one N(8) atom to form corner-sharing SiN4 tetrahedra. There are eight inequivalent N sites. In the first N site, N(3) is bonded in a distorted trigonal pyramidal geometry to one Ca(2), one Si(1), one Si(2), and one Si(4) atom. In the second N site, N(4) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Ca(2), one Si(1), and one Si(5) atom. In the third N site, N(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Si(1), one Si(2), and one Si(3) atom. In the fourth N site, N(6) is bonded in a trigonal planar geometry to one Si(1), one Si(3), and one Si(4) atom. In the fifth N site, N(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), one Si(3), and one Si(5) atom. In the sixth N site, N(8) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Si(2), and one Si(5) atom. In the seventh N site, N(1) is bonded in a trigonal planar geometry to one Ca(1), one Ca(2), one Si(2), one Si(3), and one Si(4) atom. In the eighth N site, N(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Si(4), and one Si(5) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2Si5N8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.704
_cell_length_b   7.704
_cell_length_c   9.681
_cell_angle_alpha   69.562
_cell_angle_beta   69.562
_cell_angle_gamma   42.653
_symmetry_Int_Tables_number   1
_cell_volume   360.889
_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  0.357  0.864  0.301  1.0
  Ca  Ca1  1  0.864  0.357  0.801  1.0
  Ca  Ca2  1  0.764  0.236  0.498  1.0
  Ca  Ca3  1  0.236  0.764  0.998  1.0
  Si  Si4  1  0.858  0.853  0.374  1.0
  Si  Si5  1  0.853  0.858  0.874  1.0
  Si  Si6  1  0.571  0.154  0.132  1.0
  Si  Si7  1  0.154  0.571  0.632  1.0
  Si  Si8  1  0.251  0.258  0.437  1.0
  Si  Si9  1  0.258  0.251  0.937  1.0
  Si  Si10  1  0.966  0.546  0.182  1.0
  Si  Si11  1  0.546  0.966  0.682  1.0
  Si  Si12  1  0.864  0.251  0.147  1.0
  Si  Si13  1  0.251  0.864  0.647  1.0
  N  N14  1  0.279  0.313  0.084  1.0
  N  N15  1  0.313  0.279  0.584  1.0
  N  N16  1  0.789  0.474  0.227  1.0
  N  N17  1  0.474  0.789  0.727  1.0
  N  N18  1  0.848  0.819  0.565  1.0
  N  N19  1  0.819  0.848  0.065  1.0
  N  N20  1  0.978  0.983  0.282  1.0
  N  N21  1  0.983  0.978  0.782  1.0
  N  N22  1  0.551  0.056  0.324  1.0
  N  N23  1  0.056  0.551  0.824  1.0
  N  N24  1  0.037  0.553  0.330  1.0
  N  N25  1  0.553  0.037  0.830  1.0
  N  N26  1  0.138  0.120  0.504  1.0
  N  N27  1  0.120  0.138  0.004  1.0
  N  N28  1  0.346  0.627  0.571  1.0
  N  N29  1  0.627  0.346  0.071  1.0
[/CIF]
.