FeOOH crystallizes in the triclinic P1 space group. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 51-52°. In the second Fe site, Fe(2) is bonded in a 6-coordinate geometry to one O(2), one O(6), two equivalent O(1), and two equivalent O(7) atoms. In the third Fe site, Fe(3) is bonded to one O(3), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the fourth Fe site, Fe(4) is bonded to one O(4), one O(8), two equivalent O(3), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 51-52°. There are four 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(3) atom. In the third H site, H(3) is bonded in a single-bond geometry to one O(4) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(6) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Fe(1), two equivalent Fe(2), and one H(1) atom. In the second O site, O(2) is bonded in a trigonal non-coplanar 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(3), two equivalent Fe(4), and one H(2) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Fe(4), two equivalent Fe(3), and one H(3) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Fe(2), two equivalent Fe(4), and one H(4) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Fe(3) and two equivalent Fe(2) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms.
FeOOH crystallizes in the triclinic P1 space group. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 51-52°. The Fe(1)-O(1) bond length is 2.29 Å. The Fe(1)-O(5) bond length is 1.97 Å. There is one shorter (2.02 Å) and one longer (2.04 Å) Fe(1)-O(2) bond length. There is one shorter (2.06 Å) and one longer (2.08 Å) Fe(1)-O(8) bond length. In the second Fe site, Fe(2) is bonded in a 6-coordinate geometry to one O(2), one O(6), two equivalent O(1), and two equivalent O(7) atoms. The Fe(2)-O(2) bond length is 1.95 Å. The Fe(2)-O(6) bond length is 2.47 Å. There is one shorter (2.06 Å) and one longer (2.13 Å) Fe(2)-O(1) bond length. There is one shorter (1.96 Å) and one longer (1.97 Å) Fe(2)-O(7) bond length. In the third Fe site, Fe(3) is bonded to one O(3), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 52°. The Fe(3)-O(3) bond length is 2.15 Å. The Fe(3)-O(7) bond length is 1.94 Å. Both Fe(3)-O(4) bond lengths are 2.16 Å. There is one shorter (1.96 Å) and one longer (1.97 Å) Fe(3)-O(5) bond length. In the fourth Fe site, Fe(4) is bonded to one O(4), one O(8), two equivalent O(3), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 51-52°. The Fe(4)-O(4) bond length is 2.14 Å. The Fe(4)-O(8) bond length is 1.89 Å. There is one shorter (2.11 Å) and one longer (2.12 Å) Fe(4)-O(3) bond length. There is one shorter (2.05 Å) and one longer (2.06 Å) Fe(4)-O(6) bond length. There are four 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(3) atom. The H(2)-O(3) bond length is 0.97 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(4) atom. The H(3)-O(4) bond length is 0.97 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(6) atom. The H(4)-O(6) bond length is 0.99 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Fe(1), two equivalent Fe(2), and one H(1) atom. In the second O site, O(2) is bonded in a trigonal non-coplanar 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(3), two equivalent Fe(4), and one H(2) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Fe(4), two equivalent Fe(3), and one H(3) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Fe(2), two equivalent Fe(4), and one H(4) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Fe(3) and two equivalent Fe(2) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms.