Ab initio and density functional study of the geometrical, electronic and vibrational properties of 3,4'-bi-1,2,4-triazole.

The conventional ab initio method at the closed restricted Hartree-Fock level (RHF) and the density functional theory (DFT) approach at the B3-LYP level, using the 6-31+G* basis set, are applied to predict the molecular structure and the energetic and the vibrational properties (harmonic wave numbers, force fields and potential energy distributions) of the 3,4'-bi-1,2,4-triazole and of two deuterated derivatives (ND and ND(CD)(3)). The theoretical results are compared to the Raman and infrared vibrational data. Using both methods, there is a very good agreement between theory and experiment concerning not only the wave numbers but also the isotopic shifts. This accordance allows us to validate the calculated structure of bTA. This molecule is characterized by an aromatic structure in which two triazolic rings are linked by a CN bond, intermediary between a single and double bond, in a planar conformation. From a methodological point of view, the B3-LYP method predicts more accurate structure and harmonic vibrational wave numbers than the RHF method.

[Characterization and structural approach to crystalline La2O3-MgO-B2O3]. / Caractérisation et approche structurale de verres du systeme La2O3-MgO-B2O3.

In this paper, a vitreous domain of the ternary system: xLa2O3-yMgO-zB2O3 characterised by X-ray diffraction is shown. Structural approach using vibrational spectroscopy and optical probe is realized for some of these glasses and compared to crystalline LaMgB5O10.

Vibrational study and fluorescence bands in the FT-Raman spectra of Ca(10-x)Pb(x)(PO4)6(OH)2 compounds.

About 40 apatitic compounds, stoichiometric or not, with different substitutions like lead, sodium and cadmium were investigated using infrared, Raman and FT-Raman spectroscopies. In the Ca(10-x)Pb(x)(PO4)6(OH)2 sequence (x runs from 0 to 10), the evolution of the fluorescence bands observed by FT-Raman, only with stoichiometric entities apatites, is mainly regarded and explained. Important spectral changes concerning the OH- and the PO4(3-) entities occur when 4 < or = x < or = 7. The intensity ratio of the two components of the v1 PO4(3-) mode is shown to be a suitable method to determine the lead content. The weak OH...O hydrogen bonds involving the OH- ions, of which the disorder is discussed, are different for the lead and calcium hydroxyapatites. The evolution of the fluorescence bands, as well as the splitting of the v(OH) mode, are due to the lead distribution in the two sites, with a preference for sites II, of the hydroxyapatite structure. The effect of temperature is also reported.

Raman Study of Aluminum Chloride-Dimethylsulfone Solutions.

The Raman spectra of AlCl(3)-LiCl-dimethylsulfone mixtures with different molar compositions have been recorded as a solid (300 K) and as a melt (400 K). In any case, only AlCl(4)(-) ion lines at 120, 179, and 347 cm(-)(1) were observed; we were unable to detect any other chloroaluminate species. Furthermore, some bands assigned to the Al[(CH(3))(2)SO(2)](3)(3+) octahedral coordination compound are evidence for a high AlCl(3) content.