data_KMg4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.59
_cell_length_b   6.59
_cell_length_c   6.59
_cell_angle_alpha   109.47
_cell_angle_beta   109.47
_cell_angle_gamma   109.47
_symmetry_Int_Tables_number   1
_chemical_formula_structural   KMg4
_chemical_formula_sum   'K1 Mg4'
_cell_volume   220.4
_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
  K  K0  1  0.0  0.0  0.0  1.0
  Mg  Mg1  1  0.9  0.1  0.9  1.0
  Mg  Mg2  1  0.9  0.9  0.9  1.0
  Mg  Mg3  1  0.9  0.9  0.1  1.0
  Mg  Mg4  1  0.1  0.9  0.9  1.0

data_KMg4
_symmetry_space_group_name_H-M   R3m
_cell_length_a   10.76
_cell_length_b   10.76
_cell_length_c   6.59
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   KMg4
_chemical_formula_sum   'K3 Mg12'
_cell_volume   661.21
_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+2/3, y+1/3, z+1/3'
  8  '-y+2/3, x-y+1/3, z+1/3'
  9  '-x+y+2/3, -x+1/3, z+1/3'
  10  '-y+2/3, -x+1/3, z+1/3'
  11  '-x+y+2/3, y+1/3, z+1/3'
  12  'x+2/3, x-y+1/3, z+1/3'
  13  'x+1/3, y+2/3, z+2/3'
  14  '-y+1/3, x-y+2/3, z+2/3'
  15  '-x+y+1/3, -x+2/3, z+2/3'
  16  '-y+1/3, -x+2/3, z+2/3'
  17  '-x+y+1/3, y+2/3, z+2/3'
  18  'x+1/3, x-y+2/3, z+2/3'
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
  K  K0  3  0.0  0.0  0.0  1.0
  Mg  Mg1  9  0.13  0.06  0.97  1.0
  Mg  Mg2  3  0.0  0.0  0.9  1.0

K Mg Mg Mg Mg
K Mg Mg Mg Mg 0 2 - - - 0 1 - o - 0 3 - - o 0 4 o - - 1 2 o - o 2 3 o o + 2 4 + o o 
KMg4 is Tungsten structured and crystallizes in the trigonal R3m space group. The structure is zero-dimensional and consists of three KMg4 clusters. K(1) is bonded in a single-bond geometry to one Mg(2) and three equivalent Mg(1) atoms. The K(1)-Mg(2) bond length is 0.64 Å. All K(1)-Mg(1) bond lengths are 1.23 Å. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a distorted single-bond geometry to one K(1) atom. In the second Mg site, Mg(2) is bonded in a single-bond geometry to one K(1) atom.