data_MgNbV4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.08
_cell_length_b   5.08
_cell_length_c   5.08
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   MgNbV4
_chemical_formula_sum   'Mg1 Nb1 V4'
_cell_volume   92.81
_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
  Mg  Mg0  1  0.0  0.0  0.0  1.0
  Nb  Nb1  1  0.39  0.39  0.39  1.0
  V  V2  1  0.47  0.72  0.47  1.0
  V  V3  1  0.72  0.47  0.47  1.0
  V  V4  1  0.72  0.72  0.72  1.0
  V  V5  1  0.47  0.47  0.72  1.0

data_MgNbV4
_symmetry_space_group_name_H-M   R3m
_cell_length_a   5.08
_cell_length_b   5.08
_cell_length_c   12.45
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   MgNbV4
_chemical_formula_sum   'Mg3 Nb3 V12'
_cell_volume   278.43
_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
  Mg  Mg0  3  0.0  0.0  0.0  1.0
  Nb  Nb1  3  0.0  0.0  0.61  1.0
  V  V2  9  0.08  0.17  0.45  1.0
  V  V3  3  0.0  0.0  0.28  1.0

Mg Nb V V V V
MgNbV4 crystallizes in the trigonal R3m space group. Mg(1) is bonded in a 16-coordinate geometry to three equivalent Nb(1), four equivalent V(2), and nine equivalent V(1) atoms. All Mg(1)-Nb(1) bond lengths are 3.02 Å. There are three shorter (3.00 Å) and one longer (3.51 Å) Mg(1)-V(2) bond length. There are six shorter (3.01 Å) and three longer (3.50 Å) Mg(1)-V(1) bond lengths. Nb(1) is bonded to three equivalent Mg(1), three equivalent V(2), and six equivalent V(1) atoms to form a mixture of distorted corner and edge-sharing NbMg3V9 cuboctahedra. All Nb(1)-V(2) bond lengths are 2.93 Å. There are three shorter (2.14 Å) and three longer (3.07 Å) Nb(1)-V(1) bond lengths. There are two inequivalent V sites. In the first V site, V(2) is bonded in a 10-coordinate geometry to four equivalent Mg(1), three equivalent Nb(1), and three equivalent V(1) atoms. All V(2)-V(1) bond lengths are 2.19 Å. In the second V site, V(1) is bonded in a 2-coordinate geometry to three equivalent Mg(1), two equivalent Nb(1), one V(2), and two equivalent V(1) atoms. Both V(1)-V(1) bond lengths are 1.27 Å.