FeOOH crystallizes in the orthorhombic Pmc2_1 space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 54-55°. In the second Fe site, Fe(2) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 54-55°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(4) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(2) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Fe(2) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Fe(1), two equivalent Fe(2), and one H(1) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Fe(2), two equivalent Fe(1), and one H(2) atom.
FeOOH crystallizes in the orthorhombic Pmc2_1 space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 54-55°. The Fe(1)-O(1) bond length is 1.92 Å. The Fe(1)-O(3) bond length is 2.03 Å. Both Fe(1)-O(2) bond lengths are 1.99 Å. Both Fe(1)-O(4) bond lengths are 2.11 Å. In the second Fe site, Fe(2) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 54-55°. The Fe(2)-O(2) bond length is 1.95 Å. The Fe(2)-O(4) bond length is 2.11 Å. Both Fe(2)-O(1) bond lengths are 1.99 Å. Both Fe(2)-O(3) bond lengths are 2.14 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(3) atom. The H(1)-O(3) bond length is 0.99 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(4) atom. The H(2)-O(4) bond length is 1.00 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(2) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Fe(2) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Fe(1), two equivalent Fe(2), and one H(1) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Fe(2), two equivalent Fe(1), and one H(2) atom.