data_FeO
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.08
_cell_length_b   3.08
_cell_length_c   3.08
_cell_angle_alpha   117.27
_cell_angle_beta   117.27
_cell_angle_gamma   94.8
_symmetry_Int_Tables_number   1
_chemical_formula_structural   FeO
_chemical_formula_sum   'Fe1 O1'
_cell_volume   21.39
_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
  Fe  Fe0  1  0.0  0.0  0.08  1.0
  O  O1  1  0.0  0.0  0.0  1.0

data_FeO
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.17
_cell_length_b   4.53
_cell_length_c   3.08
_cell_angle_alpha   90.0
_cell_angle_beta   132.6
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   FeO
_chemical_formula_sum   'Fe2 O2'
_cell_volume   42.78
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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
  Fe  Fe0  2  0.0  0.0  0.92  1.0
  O  O1  2  0.0  0.0  0.0  1.0

Fe O
Fe O 0 1 o o o 
FeO is alpha carbon monoxide-like structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two iron(1+), hydroxy- molecules. Fe(1) is bonded in a single-bond geometry to one O(1) atom. The Fe(1)-O(1) bond length is 0.26 Å. O(1) is bonded in a single-bond geometry to one Fe(1) atom.