FeOOH crystallizes in the monoclinic C2/m space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(4), and three equivalent O(1) atoms to form a mixture of distorted edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 53-54°. In the second Fe site, Fe(2) is bonded to one O(4), two equivalent O(3), and three equivalent O(2) atoms to form a mixture of distorted edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 53-54°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Fe(1) and one H(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to three equivalent Fe(2) and one H(2) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(2) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(1) atoms.
FeOOH crystallizes in the monoclinic C2/m space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(4), and three equivalent O(1) atoms to form a mixture of distorted edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 53-54°. The Fe(1)-O(3) bond length is 1.96 Å. Both Fe(1)-O(4) bond lengths are 1.97 Å. There is one shorter (2.15 Å) and two longer (2.16 Å) Fe(1)-O(1) bond lengths. In the second Fe site, Fe(2) is bonded to one O(4), two equivalent O(3), and three equivalent O(2) atoms to form a mixture of distorted edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 53-54°. The Fe(2)-O(4) bond length is 1.93 Å. Both Fe(2)-O(3) bond lengths are 1.97 Å. There are two shorter (2.15 Å) and one longer (2.17 Å) Fe(2)-O(2) bond length. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) atom. The H(1)-O(1) bond length is 0.97 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) atom. The H(2)-O(2) bond length is 0.97 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Fe(1) and one H(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to three equivalent Fe(2) and one H(2) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(2) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(1) atoms.