Current Journal of Applied Science and Technology

Theoretical Study of Cluster Ions Existing in Vapours over Cesium Bromide and Iodide

Stanley F. Mwanga *

Department of Materials, Energy Science and Engineering, Nelson Mandela African Institution of Science and Technology (NM-AIST), Arusha, Tanzania

Tatiana P. Pogrebnaya

Department of Materials, Energy Science and Engineering, Nelson Mandela African Institution of Science and Technology (NM-AIST), Arusha, Tanzania

Alexander M. Pogrebnoi

Department of Materials, Energy Science and Engineering, Nelson Mandela African Institution of Science and Technology (NM-AIST), Arusha, Tanzania

*Author to whom correspondence should be addressed.

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Abstract

The properties of ions Cs₂X⁺, Cs₃X₂⁺, CsX₂⁻, and Cs₂X₃⁻ (X = Br or I) have been studied using the density functional theory and Möller–Plesset perturbation theory of the 2^nd and 4^th order. For all species the equilibrium geometrical configurations and vibration frequencies were determined. Different isomers of pentaatomic ions were found to exist: the linear (D_∞h), V-shaped (C_2v), kite-shaped (C_2v) and bipyramidal (D_3h). The relative abundances of isomers were calculated for temperatures between 700 K and 1600 K. It was found that at about 800 K, the amount of different isomers was comparable for Cs₃Br₂⁺, Cs₃I₂⁺ and Cs₂I₃⁻ ions, while for Cs₂Br₃⁻ the linear isomer was proved to be predominant. The enthalpies of dissociation reactions with elimination of CsX molecules and the enthalpies of formation of ions were determined.

Keywords: Cluster ions, cesium bromide, cesium iodide, isomers, enthalpies of formation of ions, enthalpies of dissociation reactions

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