The crystal structure described by Nd2Fe20Si2C crystallizes in the triclinic P-1 space group. Nd(1) is bonded in a distorted single-bond geometry to one Fe(10), one Fe(11), two equivalent Fe(3), two equivalent Fe(4), two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), two equivalent Fe(8), two equivalent Fe(9), and one C(1) atom. There are eleven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a single-bond geometry to one Fe(10), one Fe(11), one Fe(3), one Fe(4), one Fe(5), one Fe(7), one Fe(8), one Fe(9), and one C(1) atom. In the second Fe site, Fe(2) is bonded in a single-bond geometry to one Fe(10), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Fe(8), one Fe(9), one Si(1), and one C(1) atom. In the third Fe site, Fe(3) is bonded to two equivalent Nd(1), one Fe(1), one Fe(10), one Fe(11), one Fe(2), one Fe(4), one Fe(5), one Fe(6), one Fe(9), and two equivalent Fe(7) atoms to form distorted FeNd2Fe10 cuboctahedra that share  a cornercorner with one Fe(10)Nd2Fe10 cuboctahedra, corners with two equivalent Fe(3)Nd2Fe10 cuboctahedra, corners with two equivalent C(1)Nd2Fe4 octahedra,  an edgeedge with one Fe(11)Nd2Fe10 cuboctahedra,  an edgeedge with one C(1)Nd2Fe4 octahedra,  a faceface with one Fe(10)Nd2Fe10 cuboctahedra,  a faceface with one Fe(11)Nd2Fe10 cuboctahedra, and  a faceface with one Fe(3)Nd2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles range from 27-71°. In the fourth Fe site, Fe(4) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(10), one Fe(2), one Fe(3), one Fe(5), one Fe(6), one Fe(9), two equivalent Fe(8), and one Si(1) atom. In the fifth Fe site, Fe(5) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(11), one Fe(3), one Fe(4), one Fe(7), one Fe(8), one Fe(9), two equivalent Fe(6), and one Si(2) atom. In the sixth Fe site, Fe(6) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(2), one Fe(3), one Fe(4), one Fe(7), one Fe(8), one Fe(9), two equivalent Fe(5), one Si(1), and one Si(2) atom. In the seventh Fe site, Fe(7) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(11), one Fe(2), one Fe(5), one Fe(6), one Fe(8), one Fe(9), two equivalent Fe(3), and one Si(2) atom. In the eighth Fe site, Fe(8) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(2), one Fe(5), one Fe(6), one Fe(7), one Fe(9), two equivalent Fe(4), one Si(1), and one Si(2) atom. In the ninth Fe site, Fe(9) is bonded in a 14-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(10), one Fe(11), one Fe(2), one Fe(3), one Fe(4), one Fe(5), one Fe(6), one Fe(7), one Fe(8), one Si(1), and one Si(2) atom. In the tenth Fe site, Fe(10) is bonded to two equivalent Nd(1), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), and two equivalent Fe(9) atoms to form distorted FeNd2Fe10 cuboctahedra that share corners with two equivalent Fe(11)Nd2Fe10 cuboctahedra, corners with two equivalent Fe(3)Nd2Fe10 cuboctahedra, faces with two equivalent Fe(11)Nd2Fe10 cuboctahedra, faces with two equivalent Fe(3)Nd2Fe10 cuboctahedra, and faces with two equivalent C(1)Nd2Fe4 octahedra. In the eleventh Fe site, Fe(11) is bonded to two equivalent Nd(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(7), and two equivalent Fe(9) atoms to form distorted FeNd2Fe10 cuboctahedra that share corners with two equivalent Fe(10)Nd2Fe10 cuboctahedra, edges with two equivalent Fe(3)Nd2Fe10 cuboctahedra, edges with two equivalent C(1)Nd2Fe4 octahedra, faces with two equivalent Fe(10)Nd2Fe10 cuboctahedra, and faces with two equivalent Fe(3)Nd2Fe10 cuboctahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to two equivalent Fe(2), two equivalent Fe(4), two equivalent Fe(6), two equivalent Fe(8), and two equivalent Fe(9) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), two equivalent Fe(8), and two equivalent Fe(9) atoms. C(1) is bonded to two equivalent Nd(1), two equivalent Fe(1), and two equivalent Fe(2) atoms to form CNd2Fe4 octahedra that share corners with four equivalent Fe(3)Nd2Fe10 cuboctahedra, edges with two equivalent Fe(11)Nd2Fe10 cuboctahedra, edges with two equivalent Fe(3)Nd2Fe10 cuboctahedra, and faces with two equivalent Fe(10)Nd2Fe10 cuboctahedra. is represented by the CIF card [CIF]
data_Nd2Fe20Si2C
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.395
_cell_length_b   7.845
_cell_length_c   7.820
_cell_angle_alpha   100.468
_cell_angle_beta   114.323
_cell_angle_gamma   65.662
_symmetry_Int_Tables_number   1
_cell_volume   325.722
_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
  Nd  Nd0  1  0.375  0.750  0.253  1.0
  Nd  Nd1  1  0.625  0.250  0.747  1.0
  Fe  Fe2  1  0.179  0.582  0.826  1.0
  Fe  Fe3  1  0.435  0.324  0.080  1.0
  Fe  Fe4  1  0.271  0.420  0.332  1.0
  Fe  Fe5  1  0.857  0.834  0.918  1.0
  Fe  Fe6  1  0.193  0.167  0.422  1.0
  Fe  Fe7  1  0.438  0.920  0.671  1.0
  Fe  Fe8  1  0.257  0.676  0.577  1.0
  Fe  Fe9  1  0.858  0.078  0.175  1.0
  Fe  Fe10  1  0.821  0.418  0.174  1.0
  Fe  Fe11  1  0.565  0.676  0.920  1.0
  Fe  Fe12  1  0.729  0.580  0.668  1.0
  Fe  Fe13  1  0.143  0.166  0.082  1.0
  Fe  Fe14  1  0.807  0.833  0.578  1.0
  Fe  Fe15  1  0.562  0.080  0.329  1.0
  Fe  Fe16  1  0.743  0.324  0.423  1.0
  Fe  Fe17  1  0.142  0.922  0.825  1.0
  Fe  Fe18  1  0.123  0.248  0.749  1.0
  Fe  Fe19  1  0.877  0.752  0.251  1.0
  Fe  Fe20  1  0.000  0.500  0.000  1.0
  Fe  Fe21  1  0.000  0.500  0.500  1.0
  Si  Si22  1  0.500  0.000  0.000  1.0
  Si  Si23  1  0.000  0.000  0.500  1.0
  C  C24  1  0.500  0.500  0.000  1.0
[/CIF]
.
The crystal structure described by Nd2Fe20Si2C crystallizes in the triclinic P-1 space group. Nd(1) is bonded in a distorted single-bond geometry to one Fe(10), one Fe(11), two equivalent Fe(3), two equivalent Fe(4), two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), two equivalent Fe(8), two equivalent Fe(9), and one C(1) atom. There are eleven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a single-bond geometry to one Fe(10), one Fe(11), one Fe(3), one Fe(4), one Fe(5), one Fe(7), one Fe(8), one Fe(9), and one C(1) atom. In the second Fe site, Fe(2) is bonded in a single-bond geometry to one Fe(10), one Fe(3), one Fe(4), one Fe(6), one Fe(7), one Fe(8), one Fe(9), one Si(1), and one C(1) atom. In the third Fe site, Fe(3) is bonded to two equivalent Nd(1), one Fe(1), one Fe(10), one Fe(11), one Fe(2), one Fe(4), one Fe(5), one Fe(6), one Fe(9), and two equivalent Fe(7) atoms to form distorted FeNd2Fe10 cuboctahedra that share  a cornercorner with one Fe(10)Nd2Fe10 cuboctahedra, corners with two equivalent Fe(3)Nd2Fe10 cuboctahedra, corners with two equivalent C(1)Nd2Fe4 octahedra,  an edgeedge with one Fe(11)Nd2Fe10 cuboctahedra,  an edgeedge with one C(1)Nd2Fe4 octahedra,  a faceface with one Fe(10)Nd2Fe10 cuboctahedra,  a faceface with one Fe(11)Nd2Fe10 cuboctahedra, and  a faceface with one Fe(3)Nd2Fe10 cuboctahedra. The corner-sharing octahedral tilt angles range from 27-71°. In the fourth Fe site, Fe(4) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(10), one Fe(2), one Fe(3), one Fe(5), one Fe(6), one Fe(9), two equivalent Fe(8), and one Si(1) atom. In the fifth Fe site, Fe(5) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(11), one Fe(3), one Fe(4), one Fe(7), one Fe(8), one Fe(9), two equivalent Fe(6), and one Si(2) atom. In the sixth Fe site, Fe(6) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(2), one Fe(3), one Fe(4), one Fe(7), one Fe(8), one Fe(9), two equivalent Fe(5), one Si(1), and one Si(2) atom. In the seventh Fe site, Fe(7) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(11), one Fe(2), one Fe(5), one Fe(6), one Fe(8), one Fe(9), two equivalent Fe(3), and one Si(2) atom. In the eighth Fe site, Fe(8) is bonded in a 12-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(2), one Fe(5), one Fe(6), one Fe(7), one Fe(9), two equivalent Fe(4), one Si(1), and one Si(2) atom. In the ninth Fe site, Fe(9) is bonded in a 14-coordinate geometry to two equivalent Nd(1), one Fe(1), one Fe(10), one Fe(11), one Fe(2), one Fe(3), one Fe(4), one Fe(5), one Fe(6), one Fe(7), one Fe(8), one Si(1), and one Si(2) atom. In the tenth Fe site, Fe(10) is bonded to two equivalent Nd(1), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), two equivalent Fe(4), and two equivalent Fe(9) atoms to form distorted FeNd2Fe10 cuboctahedra that share corners with two equivalent Fe(11)Nd2Fe10 cuboctahedra, corners with two equivalent Fe(3)Nd2Fe10 cuboctahedra, faces with two equivalent Fe(11)Nd2Fe10 cuboctahedra, faces with two equivalent Fe(3)Nd2Fe10 cuboctahedra, and faces with two equivalent C(1)Nd2Fe4 octahedra. In the eleventh Fe site, Fe(11) is bonded to two equivalent Nd(1), two equivalent Fe(1), two equivalent Fe(3), two equivalent Fe(5), two equivalent Fe(7), and two equivalent Fe(9) atoms to form distorted FeNd2Fe10 cuboctahedra that share corners with two equivalent Fe(10)Nd2Fe10 cuboctahedra, edges with two equivalent Fe(3)Nd2Fe10 cuboctahedra, edges with two equivalent C(1)Nd2Fe4 octahedra, faces with two equivalent Fe(10)Nd2Fe10 cuboctahedra, and faces with two equivalent Fe(3)Nd2Fe10 cuboctahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 10-coordinate geometry to two equivalent Fe(2), two equivalent Fe(4), two equivalent Fe(6), two equivalent Fe(8), and two equivalent Fe(9) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Fe(5), two equivalent Fe(6), two equivalent Fe(7), two equivalent Fe(8), and two equivalent Fe(9) atoms. C(1) is bonded to two equivalent Nd(1), two equivalent Fe(1), and two equivalent Fe(2) atoms to form CNd2Fe4 octahedra that share corners with four equivalent Fe(3)Nd2Fe10 cuboctahedra, edges with two equivalent Fe(11)Nd2Fe10 cuboctahedra, edges with two equivalent Fe(3)Nd2Fe10 cuboctahedra, and faces with two equivalent Fe(10)Nd2Fe10 cuboctahedra. is represented by the CIF card [CIF]
data_Nd2Fe20Si2C
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.395
_cell_length_b   7.845
_cell_length_c   7.820
_cell_angle_alpha   100.468
_cell_angle_beta   114.323
_cell_angle_gamma   65.662
_symmetry_Int_Tables_number   1
_cell_volume   325.722
_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
  Nd  Nd0  1  0.375  0.750  0.253  1.0
  Nd  Nd1  1  0.625  0.250  0.747  1.0
  Fe  Fe2  1  0.179  0.582  0.826  1.0
  Fe  Fe3  1  0.435  0.324  0.080  1.0
  Fe  Fe4  1  0.271  0.420  0.332  1.0
  Fe  Fe5  1  0.857  0.834  0.918  1.0
  Fe  Fe6  1  0.193  0.167  0.422  1.0
  Fe  Fe7  1  0.438  0.920  0.671  1.0
  Fe  Fe8  1  0.257  0.676  0.577  1.0
  Fe  Fe9  1  0.858  0.078  0.175  1.0
  Fe  Fe10  1  0.821  0.418  0.174  1.0
  Fe  Fe11  1  0.565  0.676  0.920  1.0
  Fe  Fe12  1  0.729  0.580  0.668  1.0
  Fe  Fe13  1  0.143  0.166  0.082  1.0
  Fe  Fe14  1  0.807  0.833  0.578  1.0
  Fe  Fe15  1  0.562  0.080  0.329  1.0
  Fe  Fe16  1  0.743  0.324  0.423  1.0
  Fe  Fe17  1  0.142  0.922  0.825  1.0
  Fe  Fe18  1  0.123  0.248  0.749  1.0
  Fe  Fe19  1  0.877  0.752  0.251  1.0
  Fe  Fe20  1  0.000  0.500  0.000  1.0
  Fe  Fe21  1  0.000  0.500  0.500  1.0
  Si  Si22  1  0.500  0.000  0.000  1.0
  Si  Si23  1  0.000  0.000  0.500  1.0
  C  C24  1  0.500  0.500  0.000  1.0
[/CIF]
.