title: A vibrational study of the nature of hydroxyl groups chemical bonding in two aluminium hydroxides.
abstract: Lengths, strengths and valences of OH bonds in the two aluminium hydroxides gibbsite and bayerite were determined on the basis of vibrational spectral data. The uncoupled OD stretching modes in the range 2400-2800cm(-1) were recorded by means of infrared diffuse reflectance, thereby avoiding effects of surface, vibrational coupling or particle shape. The assignment of the corresponding Raman spectra resulted in the determination of harmonic wavenumbers, force constants and anharmonicity coefficients of bulk OH groups in the two minerals. OH bond lengths deduced from these data varied from 0.964A to 0.975A in gibbsite and 0.962A to 0.973A in bayerite. These lengths appear to correspond to weak H-bonds contrary to previously recognized data from X-ray diffraction and neutron diffraction studies. Finally, bond valences were calculated on the basis of these new bond lengths and discussed as a function of crystallographic structures and the nature of hydrogen bonding in these two structures.
authors.affiliation: Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564 CNRS, Nancy-Université, 405 rue de Vandoeuvre, 54600 Villers-lès-Nancy, France. Marie-Camille.Caumon@g2r.uhp-nancy.fr
authors.forename: Marie-Camille
authors.initials: MC
authors.lastname: Jodin-Caumon
authors.forename: Bernard
authors.initials: B
authors.lastname: Humbert
authors.forename: Nsoki
authors.initials: N
authors.lastname: Phambu
authors.forename: Fabien
authors.initials: F
authors.lastname: Gaboriaud
mesh_terms: D000536:Aluminum Hydroxide / Q000737:chemistry*; D006860:Hydrogen Bonding; D006878:Hydroxides / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry; D013057:Spectrum Analysis / Q000379:methods; D014732:Vibration
chemical_list: D006878:Hydroxides; D008903:Minerals; D000536:Aluminum Hydroxide