title: A vibrational spectroscopic study of hydrated Fe(3+) hydroxyl-sulfates; polymorphic minerals butlerite and parabutlerite.
abstract: Raman and infrared spectra of two polymorphous minerals with the chemical formula Fe3+(SO4)(OH)·2H2O, monoclinic butlerite and orthorhombic parabutlerite, are studied and the spectra assigned. Observed bands are attributed to the (SO4)2- stretching and bending vibrations, hydrogen bonded water molecules, stretching and bending vibrations of hydroxyl ions, water librational modes, Fe-O and Fe-OH stretching vibrations, Fe-OH bending vibrations and lattice vibrations. The O-H⋯O hydrogen bond lengths in the structures of both minerals are calculated from the wavenumbers of the stretching vibrations. One symmetrically distinct (SO4)2- unit in the structure of butlerite and two symmetrically distinct (SO4)2- units in the structure of parabutlerite are inferred from the Raman and infrared spectra. This conclusion agrees with the published crystal structures of both mineral phases.
authors.affiliation: Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, GPO Box 2434, Brisbane Queensland 4001, Australia.
authors.forename: Jiří
authors.initials: J
authors.lastname: Cejka
authors.forename: Jiří
authors.initials: J
authors.lastname: Sejkora
authors.forename: Jakub
authors.initials: J
authors.lastname: Plášil
authors.forename: Silmarilly
authors.initials: S
authors.lastname: Bahfenne
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Palmer
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D006860:Hydrogen Bonding; D006878:Hydroxides / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry* / Q000378:metabolism*; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D013431:Sulfates / Q000737:chemistry*; D014732:Vibration
chemical_list: D005290:Ferric Compounds; D006878:Hydroxides; D008903:Minerals; D013431:Sulfates; C031356:hydroxide ion