data_CaCO3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.83
_cell_length_b   5.12
_cell_length_c   6.64
_cell_angle_alpha   95.21
_cell_angle_beta   105.69
_cell_angle_gamma   90.6
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CaCO3
_chemical_formula_sum   'Ca2 C2 O6'
_cell_volume   124.85
_cell_formula_units_Z   2
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
  Ca  Ca0  1  0.85  0.45  0.64  1.0
  Ca  Ca1  1  0.13  0.05  0.72  1.0
  C  C2  1  0.41  0.59  0.8  1.0
  C  C3  1  0.58  0.91  0.56  1.0
  O  O4  1  0.92  0.56  0.07  1.0
  O  O5  1  0.06  0.94  0.3  1.0
  O  O6  1  0.03  0.48  0.57  1.0
  O  O7  1  0.95  0.02  0.79  1.0
  O  O8  1  0.43  0.9  0.71  1.0
  O  O9  1  0.55  0.6  0.65  1.0

data_CaCO3
_symmetry_space_group_name_H-M   P-1
_cell_length_a   3.83
_cell_length_b   5.12
_cell_length_c   6.64
_cell_angle_alpha   95.21
_cell_angle_beta   105.69
_cell_angle_gamma   90.6
_symmetry_Int_Tables_number   2
_chemical_formula_structural   CaCO3
_chemical_formula_sum   'Ca2 C2 O6'
_cell_volume   124.85
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-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
  Ca  Ca0  2  0.36  0.2  0.46  1.0
  C  C1  2  0.08  0.66  0.38  1.0
  O  O2  2  0.06  0.35  0.47  1.0
  O  O3  2  0.43  0.31  0.88  1.0
  O  O4  2  0.46  0.77  0.61  1.0

Ca Ca C C O O O O O O
Ca Ca C C O O O O O O 0 6 + o o 0 4 o o + 0 9 o o o 1 7 - o o 1 5 o - o 1 8 o - o 2 9 o o o 2 4 o o + 3 8 o o o 3 5 o o o 4 9 o o - 4 5 + o o 5 8 o o o 
CaCO3 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two CaCO3 clusters. Ca(1) is bonded in a distorted bent 120 degrees geometry to one O(1), one O(2), and one O(3) atom. The Ca(1)-O(1) bond length is 2.77 Å. The Ca(1)-O(2) bond length is 0.95 Å. The Ca(1)-O(3) bond length is 1.40 Å. C(1) is bonded in a distorted single-bond geometry to one O(3) atom. The C(1)-O(3) bond length is 1.27 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Ca(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Ca(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one C(1) atom.