The material structure described by Er2Si4CN6 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one N(3), one N(4), one N(5), one N(6), and two equivalent N(2) atoms to form distorted ErN6 pentagonal pyramids that share corners with two equivalent Si(1)CN3 tetrahedra, corners with two equivalent Si(2)CN3 tetrahedra, corners with three equivalent Si(3)CN3 tetrahedra, corners with three equivalent Si(4)CN3 tetrahedra,  an edgeedge with one Er(1)N6 pentagonal pyramid, and  an edgeedge with one Si(2)CN3 tetrahedra. In the second Er site, Er(2) is bonded in a 5-coordinate geometry to one N(3), one N(4), one N(5), and two equivalent N(1) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one C(1), one N(1), one N(4), and one N(6) atom to form SiCN3 tetrahedra that share corners with two equivalent Er(1)N6 pentagonal pyramids, corners with two equivalent Si(2)CN3 tetrahedra, corners with two equivalent Si(3)CN3 tetrahedra, and corners with two equivalent Si(4)CN3 tetrahedra. In the second Si site, Si(2) is bonded to one C(1), one N(2), one N(4), and one N(5) atom to form SiCN3 tetrahedra that share corners with two equivalent Er(1)N6 pentagonal pyramids, corners with two equivalent Si(1)CN3 tetrahedra, corners with two equivalent Si(3)CN3 tetrahedra, corners with two equivalent Si(4)CN3 tetrahedra, and  an edgeedge with one Er(1)N6 pentagonal pyramid. In the third Si site, Si(3) is bonded to one C(1), one N(1), one N(2), and one N(3) atom to form SiCN3 tetrahedra that share corners with three equivalent Er(1)N6 pentagonal pyramids, corners with two equivalent Si(1)CN3 tetrahedra, corners with two equivalent Si(2)CN3 tetrahedra, and corners with two equivalent Si(4)CN3 tetrahedra. In the fourth Si site, Si(4) is bonded to one C(1), one N(3), one N(5), and one N(6) atom to form SiCN3 tetrahedra that share corners with three equivalent Er(1)N6 pentagonal pyramids, corners with two equivalent Si(1)CN3 tetrahedra, corners with two equivalent Si(2)CN3 tetrahedra, and corners with two equivalent Si(3)CN3 tetrahedra. C(1) is bonded to one Si(1), one Si(2), one Si(3), and one Si(4) atom to form CSi4 tetrahedra that share corners with two equivalent N(1)Er2Si2 tetrahedra, corners with two equivalent N(2)Er2Si2 tetrahedra, corners with two equivalent N(3)Er2Si2 tetrahedra, and corners with two equivalent N(5)Er2Si2 trigonal pyramids. There are six inequivalent N sites. In the first N site, N(2) is bonded to two equivalent Er(1), one Si(2), and one Si(3) atom to form distorted NEr2Si2 tetrahedra that share  a cornercorner with one N(1)Er2Si2 tetrahedra, corners with two equivalent C(1)Si4 tetrahedra, corners with three equivalent N(3)Er2Si2 tetrahedra, corners with three equivalent N(5)Er2Si2 trigonal pyramids, and  an edgeedge with one N(2)Er2Si2 tetrahedra. In the second N site, N(3) is bonded to one Er(1), one Er(2), one Si(3), and one Si(4) atom to form distorted NEr2Si2 tetrahedra that share corners with two equivalent C(1)Si4 tetrahedra, corners with three equivalent N(1)Er2Si2 tetrahedra, corners with three equivalent N(2)Er2Si2 tetrahedra,  a cornercorner with one N(5)Er2Si2 trigonal pyramid, and  an edgeedge with one N(5)Er2Si2 trigonal pyramid. In the third N site, N(4) is bonded in a 4-coordinate geometry to one Er(1), one Er(2), one Si(1), and one Si(2) atom. In the fourth N site, N(5) is bonded to one Er(1), one Er(2), one Si(2), and one Si(4) atom to form distorted NEr2Si2 trigonal pyramids that share  a cornercorner with one N(3)Er2Si2 tetrahedra, corners with two equivalent C(1)Si4 tetrahedra, corners with two equivalent N(1)Er2Si2 tetrahedra, corners with three equivalent N(2)Er2Si2 tetrahedra, and  an edgeedge with one N(3)Er2Si2 tetrahedra. In the fifth N site, N(6) is bonded in a distorted trigonal planar geometry to one Er(1), one Si(1), and one Si(4) atom. In the sixth N site, N(1) is bonded to two equivalent Er(2), one Si(1), and one Si(3) atom to form NEr2Si2 tetrahedra that share  a cornercorner with one N(2)Er2Si2 tetrahedra, corners with two equivalent C(1)Si4 tetrahedra, corners with three equivalent N(3)Er2Si2 tetrahedra, corners with two equivalent N(5)Er2Si2 trigonal pyramids, and  an edgeedge with one N(1)Er2Si2 tetrahedra. is represented by the CIF file [CIF]
data_Er2Si4CN6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.939
_cell_length_b   5.938
_cell_length_c   11.897
_cell_angle_alpha   60.436
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   610.721
_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
  Er  Er0  1  0.087  0.341  0.918  1.0
  Er  Er1  1  0.913  0.659  0.082  1.0
  Er  Er2  1  0.587  0.659  0.582  1.0
  Er  Er3  1  0.413  0.341  0.418  1.0
  Er  Er4  1  0.934  0.669  0.595  1.0
  Er  Er5  1  0.066  0.331  0.405  1.0
  Er  Er6  1  0.434  0.331  0.905  1.0
  Er  Er7  1  0.566  0.669  0.095  1.0
  Si  Si8  1  0.287  0.835  0.920  1.0
  Si  Si9  1  0.713  0.165  0.080  1.0
  Si  Si10  1  0.787  0.165  0.580  1.0
  Si  Si11  1  0.213  0.835  0.420  1.0
  Si  Si12  1  0.272  0.323  0.659  1.0
  Si  Si13  1  0.728  0.677  0.341  1.0
  Si  Si14  1  0.772  0.677  0.841  1.0
  Si  Si15  1  0.228  0.323  0.159  1.0
  Si  Si16  1  0.020  0.995  0.749  1.0
  Si  Si17  1  0.980  0.005  0.251  1.0
  Si  Si18  1  0.520  0.005  0.751  1.0
  Si  Si19  1  0.480  0.995  0.249  1.0
  Si  Si20  1  0.295  0.798  0.677  1.0
  Si  Si21  1  0.705  0.202  0.323  1.0
  Si  Si22  1  0.795  0.202  0.823  1.0
  Si  Si23  1  0.205  0.798  0.177  1.0
  C  C24  1  0.208  0.977  0.752  1.0
  C  C25  1  0.792  0.023  0.248  1.0
  C  C26  1  0.708  0.023  0.748  1.0
  C  C27  1  0.292  0.977  0.252  1.0
  N  N28  1  0.455  0.942  0.900  1.0
  N  N29  1  0.545  0.058  0.100  1.0
  N  N30  1  0.955  0.058  0.600  1.0
  N  N31  1  0.045  0.942  0.400  1.0
  N  N32  1  0.447  0.301  0.637  1.0
  N  N33  1  0.553  0.699  0.363  1.0
  N  N34  1  0.947  0.699  0.863  1.0
  N  N35  1  0.053  0.301  0.137  1.0
  N  N36  1  0.465  0.756  0.724  1.0
  N  N37  1  0.535  0.244  0.276  1.0
  N  N38  1  0.965  0.244  0.776  1.0
  N  N39  1  0.035  0.756  0.224  1.0
  N  N40  1  0.209  0.494  0.500  1.0
  N  N41  1  0.791  0.506  0.500  1.0
  N  N42  1  0.709  0.506  1.000  1.0
  N  N43  1  0.291  0.494  0.000  1.0
  N  N44  1  0.236  0.481  0.747  1.0
  N  N45  1  0.764  0.519  0.253  1.0
  N  N46  1  0.736  0.519  0.753  1.0
  N  N47  1  0.264  0.481  0.247  1.0
  N  N48  1  0.291  0.959  0.509  1.0
  N  N49  1  0.709  0.041  0.491  1.0
  N  N50  1  0.791  0.041  0.991  1.0
  N  N51  1  0.209  0.959  0.009  1.0
[/CIF]
.
The material structure described by Er2Si4CN6 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one N(3), one N(4), one N(5), one N(6), and two equivalent N(2) atoms to form distorted ErN6 pentagonal pyramids that share corners with two equivalent Si(1)CN3 tetrahedra, corners with two equivalent Si(2)CN3 tetrahedra, corners with three equivalent Si(3)CN3 tetrahedra, corners with three equivalent Si(4)CN3 tetrahedra,  an edgeedge with one Er(1)N6 pentagonal pyramid, and  an edgeedge with one Si(2)CN3 tetrahedra. In the second Er site, Er(2) is bonded in a 5-coordinate geometry to one N(3), one N(4), one N(5), and two equivalent N(1) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one C(1), one N(1), one N(4), and one N(6) atom to form SiCN3 tetrahedra that share corners with two equivalent Er(1)N6 pentagonal pyramids, corners with two equivalent Si(2)CN3 tetrahedra, corners with two equivalent Si(3)CN3 tetrahedra, and corners with two equivalent Si(4)CN3 tetrahedra. In the second Si site, Si(2) is bonded to one C(1), one N(2), one N(4), and one N(5) atom to form SiCN3 tetrahedra that share corners with two equivalent Er(1)N6 pentagonal pyramids, corners with two equivalent Si(1)CN3 tetrahedra, corners with two equivalent Si(3)CN3 tetrahedra, corners with two equivalent Si(4)CN3 tetrahedra, and  an edgeedge with one Er(1)N6 pentagonal pyramid. In the third Si site, Si(3) is bonded to one C(1), one N(1), one N(2), and one N(3) atom to form SiCN3 tetrahedra that share corners with three equivalent Er(1)N6 pentagonal pyramids, corners with two equivalent Si(1)CN3 tetrahedra, corners with two equivalent Si(2)CN3 tetrahedra, and corners with two equivalent Si(4)CN3 tetrahedra. In the fourth Si site, Si(4) is bonded to one C(1), one N(3), one N(5), and one N(6) atom to form SiCN3 tetrahedra that share corners with three equivalent Er(1)N6 pentagonal pyramids, corners with two equivalent Si(1)CN3 tetrahedra, corners with two equivalent Si(2)CN3 tetrahedra, and corners with two equivalent Si(3)CN3 tetrahedra. C(1) is bonded to one Si(1), one Si(2), one Si(3), and one Si(4) atom to form CSi4 tetrahedra that share corners with two equivalent N(1)Er2Si2 tetrahedra, corners with two equivalent N(2)Er2Si2 tetrahedra, corners with two equivalent N(3)Er2Si2 tetrahedra, and corners with two equivalent N(5)Er2Si2 trigonal pyramids. There are six inequivalent N sites. In the first N site, N(2) is bonded to two equivalent Er(1), one Si(2), and one Si(3) atom to form distorted NEr2Si2 tetrahedra that share  a cornercorner with one N(1)Er2Si2 tetrahedra, corners with two equivalent C(1)Si4 tetrahedra, corners with three equivalent N(3)Er2Si2 tetrahedra, corners with three equivalent N(5)Er2Si2 trigonal pyramids, and  an edgeedge with one N(2)Er2Si2 tetrahedra. In the second N site, N(3) is bonded to one Er(1), one Er(2), one Si(3), and one Si(4) atom to form distorted NEr2Si2 tetrahedra that share corners with two equivalent C(1)Si4 tetrahedra, corners with three equivalent N(1)Er2Si2 tetrahedra, corners with three equivalent N(2)Er2Si2 tetrahedra,  a cornercorner with one N(5)Er2Si2 trigonal pyramid, and  an edgeedge with one N(5)Er2Si2 trigonal pyramid. In the third N site, N(4) is bonded in a 4-coordinate geometry to one Er(1), one Er(2), one Si(1), and one Si(2) atom. In the fourth N site, N(5) is bonded to one Er(1), one Er(2), one Si(2), and one Si(4) atom to form distorted NEr2Si2 trigonal pyramids that share  a cornercorner with one N(3)Er2Si2 tetrahedra, corners with two equivalent C(1)Si4 tetrahedra, corners with two equivalent N(1)Er2Si2 tetrahedra, corners with three equivalent N(2)Er2Si2 tetrahedra, and  an edgeedge with one N(3)Er2Si2 tetrahedra. In the fifth N site, N(6) is bonded in a distorted trigonal planar geometry to one Er(1), one Si(1), and one Si(4) atom. In the sixth N site, N(1) is bonded to two equivalent Er(2), one Si(1), and one Si(3) atom to form NEr2Si2 tetrahedra that share  a cornercorner with one N(2)Er2Si2 tetrahedra, corners with two equivalent C(1)Si4 tetrahedra, corners with three equivalent N(3)Er2Si2 tetrahedra, corners with two equivalent N(5)Er2Si2 trigonal pyramids, and  an edgeedge with one N(1)Er2Si2 tetrahedra. is represented by the CIF file [CIF]
data_Er2Si4CN6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.939
_cell_length_b   5.938
_cell_length_c   11.897
_cell_angle_alpha   60.436
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   610.721
_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
  Er  Er0  1  0.087  0.341  0.918  1.0
  Er  Er1  1  0.913  0.659  0.082  1.0
  Er  Er2  1  0.587  0.659  0.582  1.0
  Er  Er3  1  0.413  0.341  0.418  1.0
  Er  Er4  1  0.934  0.669  0.595  1.0
  Er  Er5  1  0.066  0.331  0.405  1.0
  Er  Er6  1  0.434  0.331  0.905  1.0
  Er  Er7  1  0.566  0.669  0.095  1.0
  Si  Si8  1  0.287  0.835  0.920  1.0
  Si  Si9  1  0.713  0.165  0.080  1.0
  Si  Si10  1  0.787  0.165  0.580  1.0
  Si  Si11  1  0.213  0.835  0.420  1.0
  Si  Si12  1  0.272  0.323  0.659  1.0
  Si  Si13  1  0.728  0.677  0.341  1.0
  Si  Si14  1  0.772  0.677  0.841  1.0
  Si  Si15  1  0.228  0.323  0.159  1.0
  Si  Si16  1  0.020  0.995  0.749  1.0
  Si  Si17  1  0.980  0.005  0.251  1.0
  Si  Si18  1  0.520  0.005  0.751  1.0
  Si  Si19  1  0.480  0.995  0.249  1.0
  Si  Si20  1  0.295  0.798  0.677  1.0
  Si  Si21  1  0.705  0.202  0.323  1.0
  Si  Si22  1  0.795  0.202  0.823  1.0
  Si  Si23  1  0.205  0.798  0.177  1.0
  C  C24  1  0.208  0.977  0.752  1.0
  C  C25  1  0.792  0.023  0.248  1.0
  C  C26  1  0.708  0.023  0.748  1.0
  C  C27  1  0.292  0.977  0.252  1.0
  N  N28  1  0.455  0.942  0.900  1.0
  N  N29  1  0.545  0.058  0.100  1.0
  N  N30  1  0.955  0.058  0.600  1.0
  N  N31  1  0.045  0.942  0.400  1.0
  N  N32  1  0.447  0.301  0.637  1.0
  N  N33  1  0.553  0.699  0.363  1.0
  N  N34  1  0.947  0.699  0.863  1.0
  N  N35  1  0.053  0.301  0.137  1.0
  N  N36  1  0.465  0.756  0.724  1.0
  N  N37  1  0.535  0.244  0.276  1.0
  N  N38  1  0.965  0.244  0.776  1.0
  N  N39  1  0.035  0.756  0.224  1.0
  N  N40  1  0.209  0.494  0.500  1.0
  N  N41  1  0.791  0.506  0.500  1.0
  N  N42  1  0.709  0.506  1.000  1.0
  N  N43  1  0.291  0.494  0.000  1.0
  N  N44  1  0.236  0.481  0.747  1.0
  N  N45  1  0.764  0.519  0.253  1.0
  N  N46  1  0.736  0.519  0.753  1.0
  N  N47  1  0.264  0.481  0.247  1.0
  N  N48  1  0.291  0.959  0.509  1.0
  N  N49  1  0.709  0.041  0.491  1.0
  N  N50  1  0.791  0.041  0.991  1.0
  N  N51  1  0.209  0.959  0.009  1.0
[/CIF]
.