Theoretical kinetic studies of Venus chemistry. Formation and destruction of SCl, SCl2, and HSCl

TL;DR

This study uses advanced quantum chemistry and kinetic theory to analyze the formation and destruction pathways of sulfur-chlorine compounds in Venus's atmosphere, providing insights into their potential roles and behaviors.

Contribution

It presents the first detailed kinetic characterization of SCl, SCl2, and HSCl reactions relevant to Venus's atmospheric chemistry using high-level ab initio methods.

Findings

Addition-elimination reactions can compete with abstraction reactions due to sulfur's hypervalency.

Reaction pathways involve complex intermediates with recoupled pair bonding.

Quantitative rate coefficients for key reactions are predicted.

Abstract

Accurate and thorough characterization of the chemistry of compounds containing the third-row elements sulfur and chlorine is critical for modeling the composition of the atmosphere of Venus. We have used a combination of ab initio quantum chemistry and kinetic theory to characterize a group of nine exothermic reactions that involve the exotic sulfur-chlorine species SCl, SCl2, and HSCl, which are thought to be present in trace quantities in the atmosphere of Venus and are included to various degrees in the published atmospheric models. Reaction pathways were characterized with coupled cluster theory at the RCCSD(T) level with triple zeta quality correlation consistent basis sets. For reactions with barriers that lie above the reactant asymptote, the barrier height was extrapolated to the RCCSD(T) complete basis set level via single-point calculations with quadruple and quintuple zeta quality sets. Rate coefficients were predicted with capture theory and transition state theory as appropriate. We have found that in some cases addition-elimination reactions can compete with abstraction reactions due to the tendency of sulfur to form hypervalent compounds and intermediates via recoupled pair bonding.