Vibrational spectra of magnesia cement, phase 3

Infrared and Raman spectra of magnesia cement, Mg-2(OH)BCl . 4H(2)O (phase 3), were observed at room temperature. The formation process of phase 3 was investigated from the change in OH- stretching vibrations by comparison wi th those of phase 5. Broad infrared bands were observed at similar to 1300 cm(-1) (H system) and 1050 cm(-1) (D system) with some structures in phase 3, which is considered to result from the coupling of the OH stretching Vib ration with lattice modes. The vibrational analysis was carried out for the lattice vibrations (translational modes) of phase 3, assuming OH- and H2O as the point masses on the basis of the valence force field. The Raman inte nsity was analyzed by the modified many-body model. The infrared intensity was also analyzed using known parameters, by adding the dipole moments due to electric charges of ions, the orientation of permanent dipoles (OH- and H2O) and induced dipoles by electric charges. The force constants were dete rmined in consistency with the calculated wavenumbers and the calculated in frared and Raman intensities. Copyright (C) 2001 John Wiley & Sons, Ltd.