The structure described by Np3Er is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Np sites. In the first Np site, Np(1) is bonded to four equivalent Np(1), four equivalent Np(2), and four equivalent Er(1) atoms to form NpEr4Np8 cuboctahedra that share corners with twelve equivalent Np(1)Er4Np8 cuboctahedra, edges with eight equivalent Np(1)Er4Np8 cuboctahedra, edges with eight equivalent Np(2)Er4Np8 cuboctahedra, edges with eight equivalent Er(1)Np12 cuboctahedra, faces with four equivalent Np(2)Er4Np8 cuboctahedra, faces with four equivalent Er(1)Np12 cuboctahedra, and faces with ten equivalent Np(1)Er4Np8 cuboctahedra. In the second Np site, Np(2) is bonded to eight equivalent Np(1) and four equivalent Er(1) atoms to form NpEr4Np8 cuboctahedra that share corners with four equivalent Np(2)Er4Np8 cuboctahedra, corners with eight equivalent Er(1)Np12 cuboctahedra, edges with eight equivalent Np(2)Er4Np8 cuboctahedra, edges with sixteen equivalent Np(1)Er4Np8 cuboctahedra, faces with four equivalent Np(2)Er4Np8 cuboctahedra, faces with six equivalent Er(1)Np12 cuboctahedra, and faces with eight equivalent Np(1)Er4Np8 cuboctahedra. Er(1) is bonded to four equivalent Np(2) and eight equivalent Np(1) atoms to form ErNp12 cuboctahedra that share corners with four equivalent Er(1)Np12 cuboctahedra, corners with eight equivalent Np(2)Er4Np8 cuboctahedra, edges with eight equivalent Er(1)Np12 cuboctahedra, edges with sixteen equivalent Np(1)Er4Np8 cuboctahedra, faces with four equivalent Er(1)Np12 cuboctahedra, faces with six equivalent Np(2)Er4Np8 cuboctahedra, and faces with eight equivalent Np(1)Er4Np8 cuboctahedra. is represented by the CIF card [CIF]
data_ErNp3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.551
_cell_length_b   5.551
_cell_length_c   5.551
_cell_angle_alpha   131.930
_cell_angle_beta   131.930
_cell_angle_gamma   70.340
_symmetry_Int_Tables_number   1
_cell_volume   92.770
_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
  Er  Er0  1  0.000  0.000  0.000  1.0
  Np  Np1  1  0.750  0.250  0.500  1.0
  Np  Np2  1  0.250  0.750  0.500  1.0
  Np  Np3  1  0.500  0.500  0.000  1.0
[/CIF]
.
The structure described by Np3Er is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Np sites. In the first Np site, Np(1) is bonded to four equivalent Np(1), four equivalent Np(2), and four equivalent Er(1) atoms to form NpEr4Np8 cuboctahedra that share corners with twelve equivalent Np(1)Er4Np8 cuboctahedra, edges with eight equivalent Np(1)Er4Np8 cuboctahedra, edges with eight equivalent Np(2)Er4Np8 cuboctahedra, edges with eight equivalent Er(1)Np12 cuboctahedra, faces with four equivalent Np(2)Er4Np8 cuboctahedra, faces with four equivalent Er(1)Np12 cuboctahedra, and faces with ten equivalent Np(1)Er4Np8 cuboctahedra. In the second Np site, Np(2) is bonded to eight equivalent Np(1) and four equivalent Er(1) atoms to form NpEr4Np8 cuboctahedra that share corners with four equivalent Np(2)Er4Np8 cuboctahedra, corners with eight equivalent Er(1)Np12 cuboctahedra, edges with eight equivalent Np(2)Er4Np8 cuboctahedra, edges with sixteen equivalent Np(1)Er4Np8 cuboctahedra, faces with four equivalent Np(2)Er4Np8 cuboctahedra, faces with six equivalent Er(1)Np12 cuboctahedra, and faces with eight equivalent Np(1)Er4Np8 cuboctahedra. Er(1) is bonded to four equivalent Np(2) and eight equivalent Np(1) atoms to form ErNp12 cuboctahedra that share corners with four equivalent Er(1)Np12 cuboctahedra, corners with eight equivalent Np(2)Er4Np8 cuboctahedra, edges with eight equivalent Er(1)Np12 cuboctahedra, edges with sixteen equivalent Np(1)Er4Np8 cuboctahedra, faces with four equivalent Er(1)Np12 cuboctahedra, faces with six equivalent Np(2)Er4Np8 cuboctahedra, and faces with eight equivalent Np(1)Er4Np8 cuboctahedra. is represented by the CIF card [CIF]
data_ErNp3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.551
_cell_length_b   5.551
_cell_length_c   5.551
_cell_angle_alpha   131.930
_cell_angle_beta   131.930
_cell_angle_gamma   70.340
_symmetry_Int_Tables_number   1
_cell_volume   92.770
_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
  Er  Er0  1  0.000  0.000  0.000  1.0
  Np  Np1  1  0.750  0.250  0.500  1.0
  Np  Np2  1  0.250  0.750  0.500  1.0
  Np  Np3  1  0.500  0.500  0.000  1.0
[/CIF]
.