data_K2CaCu
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.16
_cell_length_b   6.16
_cell_length_c   6.16
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   K2CaCu
_chemical_formula_sum   'K2 Ca1 Cu1'
_cell_volume   165.19
_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  K2  1  0.53  0.53  0.53  1.0
  K  K3  1  0.18  0.18  0.18  1.0
  Ca  Ca0  1  0.0  0.0  0.0  1.0
  Cu  Cu1  1  0.35  0.35  0.35  1.0

data_K2CaCu
_symmetry_space_group_name_H-M   R3m
_cell_length_a   6.16
_cell_length_b   6.16
_cell_length_c   15.09
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   K2CaCu
_chemical_formula_sum   'K6 Ca3 Cu3'
_cell_volume   495.57
_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
  K  K0  3  0.0  0.0  0.47  1.0
  K  K1  3  0.0  0.0  0.82  1.0
  Ca  Ca2  3  0.0  0.0  0.0  1.0
  Cu  Cu3  3  0.0  0.0  0.65  1.0

K K Ca Cu
K2CaCu crystallizes in the trigonal R3m space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a single-bond geometry to one Cu(1) atom. The K(1)-Cu(1) bond length is 2.68 Å. In the second K site, K(2) is bonded in a distorted linear geometry to one Ca(1) and one Cu(1) atom. The K(2)-Ca(1) bond length is 2.68 Å. The K(2)-Cu(1) bond length is 2.68 Å. Ca(1) is bonded to one K(2) and three equivalent Cu(1) atoms to form distorted CaKCu3 trigonal pyramids that share  a cornercorner with one Cu(1)K2Ca3 trigonal bipyramid and corners with six equivalent Ca(1)KCu3 trigonal pyramids. All Ca(1)-Cu(1) bond lengths are 3.57 Å. Cu(1) is bonded to one K(1), one K(2), and three equivalent Ca(1) atoms to form distorted CuK2Ca3 trigonal bipyramids that share corners with six equivalent Cu(1)K2Ca3 trigonal bipyramids and  a cornercorner with one Ca(1)KCu3 trigonal pyramid.