Crystal structure of synthetic feroxyhite $\delta$-FeOOH studied with neutron diffraction

The synthetic polycrystalline sample of $\delta$-FeOOH was investigated by means of neutron diffraction. Based on these data, the parameters of the crystal structure are determined. This compound crystallizes in the hexagonal structure described by the space group P$\bar{3}$m1, in which the oxygen O$^{2-}$ ions in the 2d site form the octahedral network. The Fe$^{3+}$ ions randomly occupy the 1a (53%) and 1b (47%) sites, and the hydrogen atoms half-occupy two positions in the 2d site. The magnetic contribution to the neutron diffraction pattern is very small and does not give possibility to determine the magnetic structure.