The material structure described by FeOOH crystallizes in the monoclinic C2/m space group. Fe(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 24°. H(1,2) is bonded in a linear geometry to two equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Fe(1) atoms to form OFe4 trigonal pyramids that share corners with six equivalent O(2)Fe2H2 tetrahedra, corners with four equivalent O(1)Fe4 trigonal pyramids,  an edgeedge with one O(2)Fe2H2 tetrahedra, and edges with four equivalent O(1)Fe4 trigonal pyramids. In the second O site, O(2) is bonded to two equivalent Fe(1) and two equivalent H(1,2) atoms to form distorted OFe2H2 tetrahedra that share corners with four equivalent O(2)Fe2H2 tetrahedra, corners with six equivalent O(1)Fe4 trigonal pyramids, and  an edgeedge with one O(1)Fe4 trigonal pyramid. is represented by the CIF file [CIF]
data_FeHO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.096
_cell_length_b   3.910
_cell_length_c   6.199
_cell_angle_alpha   89.846
_cell_angle_beta   75.542
_cell_angle_gamma   90.001
_symmetry_Int_Tables_number   1
_cell_volume   72.648
_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
  Fe  Fe0  1  0.327  0.748  0.346  1.0
  Fe  Fe1  1  0.673  0.252  0.654  1.0
  H  H2  1  1.000  0.500  0.000  1.0
  H  H3  1  0.000  0.000  0.000  1.0
  O  O4  1  0.708  0.752  0.585  1.0
  O  O5  1  0.292  0.248  0.416  1.0
  O  O6  1  0.939  0.749  0.122  1.0
  O  O7  1  0.061  0.251  0.878  1.0
[/CIF]
.
The material structure described by FeOOH crystallizes in the monoclinic C2/m space group. Fe(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 24°. H(1,2) is bonded in a linear geometry to two equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Fe(1) atoms to form OFe4 trigonal pyramids that share corners with six equivalent O(2)Fe2H2 tetrahedra, corners with four equivalent O(1)Fe4 trigonal pyramids,  an edgeedge with one O(2)Fe2H2 tetrahedra, and edges with four equivalent O(1)Fe4 trigonal pyramids. In the second O site, O(2) is bonded to two equivalent Fe(1) and two equivalent H(1,2) atoms to form distorted OFe2H2 tetrahedra that share corners with four equivalent O(2)Fe2H2 tetrahedra, corners with six equivalent O(1)Fe4 trigonal pyramids, and  an edgeedge with one O(1)Fe4 trigonal pyramid. is represented by the CIF file [CIF]
data_FeHO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.096
_cell_length_b   3.910
_cell_length_c   6.199
_cell_angle_alpha   89.846
_cell_angle_beta   75.542
_cell_angle_gamma   90.001
_symmetry_Int_Tables_number   1
_cell_volume   72.648
_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
  Fe  Fe0  1  0.327  0.748  0.346  1.0
  Fe  Fe1  1  0.673  0.252  0.654  1.0
  H  H2  1  1.000  0.500  0.000  1.0
  H  H3  1  0.000  0.000  0.000  1.0
  O  O4  1  0.708  0.752  0.585  1.0
  O  O5  1  0.292  0.248  0.416  1.0
  O  O6  1  0.939  0.749  0.122  1.0
  O  O7  1  0.061  0.251  0.878  1.0
[/CIF]
.