Lattice vibration spectra .89. Near-infrared spectra of M(OH)Cl (M=Ca, Cd, Sr), Zn(OH)F, gamma-Cd(OH)(2), Sr(OH)(2), and brucite-type hydroxides M(OH)(2) (M=Mg, Ca, Mn, Fe, Co, Ni, Cd)

Near-infrared (NIR) spectra of Zn(OH)F, gamma-Cd(OH)(2), Sr(OH)(2), the isostructural M(OH)Cl (M = Ca, Cd, Sr), and the brucite-type hydroxides M(OH)(2) (M = Mg, Ca, Mn, Fe, Co, Ni, Cd) (as well as of deuterated and isotopically-diluted specimens) are recorded and assigned to overtones and combination bands of the stretching modes. The anharmonicities obtained are compared with those calculated by approximation procedures. The anharmonicities increase with both increasing strength of hydrogen bonds and decreasing M-O distances in the case of non-hydrogen-bonded OH- ions. The intensities of the respective NIR bands decrease with the increase in strength of hydrogen bonds. In the case of centrosymmetric brucite-type hydroxides, of which direct overtones are infrared-forbidden, the bands observed in the NIR region behave like overtones of uncoupled stretching modes.