Structure and thermodynamic properties of cluster ions in saturated vapour over barium dibromide

Abstract

The structure and thermodynamic properties of cluster ions detected earlier in saturated vapour over barium dibromide were studied theoretically. The equilibrium geometrical parameters and vibrational spectra were computed for the ions BaBr3−, Ba2Br3+, Ba3Br5+, Ba4Br7+ and Ba5Br9+; the DFT and MP2 methods with triple-zeta valence basis sets were used. The enthalpies of ion molecular reactions were obtained both theoretically through the total energies of participants and based on experimental data. The theoretical results were scrutinized with respect to methods of computation (DFT, MP2, and MP4). The enthalpies of formation ΔfHo(0) of the ions have been determined (in kJmol−1): −858±6 (BaBr3−); −293±10 (Ba2Br3+); −982±20 (Ba3Br5+); −1644±30 (Ba4Br7+); −2282±17 (Ba5Br9+).