Home – Home – Jornals – Journal of Structural Chemistry 2010 number 2

Nonempirical methods are used to calculate the geometric parameters, the frequencies of normal vibrations, and thermochemical characteristics of ions existing in saturated vapors over sodium bromide and iodide: Na₂X⁺, and (X = Br, I). According to the calculations, Na₂X⁺ and triatomic ions have a linear equilibrium configuration of D_∞h symmetry. Pentaatomic ions can exist in the form of three isomers: linear with D_∞h symmetry, planar cyclic with С_2v symmetry, and bipyramidal with D_3h symmetry. At a temperature of ~1000 K, and pentaatomic ions are shown to be present in vapor mainly in the form of linear isomers. The energies and enthalpies of ion molecular reactions with the participation of the above ions are calculated, and the formation enthalpies of the ions are determined, Δ_fH°(0 K): 293±2 kJ/mol (Na₂Br⁺), 354±2 kJ/mol (Na₂I⁺), -536±2 kJ/mol -458±2 kJ/mol 24±5 kJ/mol 143±5 kJ/mol -810±5 kJ/mol and -675±5 kJ/mol