Theoretical Study of Structure and Vibrational Spectra of Molecular and Ionic Clusters Existing in Vapour over Rubidium Chloride

Abstract

The geometrical structure and the vibrational spectra of dimer Rb 2 Cl 2 , trimer Rb 3 Cl 3 , tetramer Rb 4 Cl 4 molecules and heptaatomic Rb 4 Cl 3 + , Rb 3 Cl 4 ions were studied. The cluster molecules and ions had been detected in equilibrium vapour over rubidium chloride previously. The quantum chemical calculations by DFT with hybrid functional B3P86 and MP2 methods were performed. The effective core potential with Def2-TZVP (6s4p3d) basis set for rubidium atom and full electron aug-cc-pVTZ (6s5p3d2f) basis set for chlorine atom were used. The equilibrium configuration was confirmed to be rhomb of symmetry D 2h for dimer Rb 2 Cl 2 , distorted cube (T d) for tetramer Rb 4 Cl 4 and polyhedral (C 3v) for heptaatomic ions Rb 4 Cl 3 + and Rb 3 Cl 4-. For the trimer molecule Rb 3 Cl 3 two isomers have been revealed: hexagonal (D 3h) and butterfly-shaped (C 2v), the latter has lower energy and is proved to be predominant in equilibrium vapour in a broad temperature range.