data_Zr2NpNb
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.91
_cell_length_b   4.91
_cell_length_c   4.91
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Zr2NpNb
_chemical_formula_sum   'Zr2 Np1 Nb1'
_cell_volume   83.45
_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
  Zr  Zr2  1  0.2  0.2  0.2  1.0
  Zr  Zr3  1  0.73  0.73  0.73  1.0
  Np  Np1  1  0.47  0.47  0.47  1.0
  Nb  Nb0  1  0.0  0.0  0.0  1.0

data_Zr2NpNb
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.91
_cell_length_b   4.91
_cell_length_c   12.01
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Zr2NpNb
_chemical_formula_sum   'Zr6 Np3 Nb3'
_cell_volume   250.35
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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
  Zr  Zr0  3  0.0  0.0  0.27  1.0
  Zr  Zr1  3  0.0  0.0  0.8  1.0
  Np  Np2  3  0.0  0.0  0.53  1.0
  Nb  Nb3  3  0.0  0.0  0.0  1.0

Zr Zr Np Nb
Zr Zr Np Nb 0 3 o o o 0 3 o o + 0 3 + o o 0 3 o + o 0 1 - - o 0 1 - o - 0 1 o - - 0 2 - o o 0 2 o - o 0 2 o o - 0 2 o o o 1 2 o o o 1 2 o o + 1 2 o + o 1 2 + o o 1 3 o + + 1 3 + o + 1 3 + + o 1 3 + + + 2 3 o o + 2 3 o + o 2 3 + o o 
NpZr2Nb is Heusler structured and crystallizes in the trigonal R3m space group. Np(1) is bonded in a 11-coordinate geometry to four equivalent Zr(1), four equivalent Zr(2), and three equivalent Nb(1) atoms. There are three shorter (2.95 Å) and one longer (3.19 Å) Np(1)-Zr(1) bond length. There are three shorter (2.95 Å) and one longer (3.19 Å) Np(1)-Zr(2) bond length. All Np(1)-Nb(1) bond lengths are 3.26 Å. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a distorted single-bond geometry to four equivalent Np(1) and one Nb(1) atom. The Zr(1)-Nb(1) bond length is 2.43 Å. In the second Zr site, Zr(2) is bonded in a 8-coordinate geometry to four equivalent Np(1) and four equivalent Nb(1) atoms. There are three shorter (2.95 Å) and one longer (3.19 Å) Zr(2)-Nb(1) bond length. Nb(1) is bonded in a 1-coordinate geometry to three equivalent Np(1), one Zr(1), and four equivalent Zr(2) atoms.