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Chemical kinetic properties of HNgF -> HF plus Ng (Ng = Ar, Kr, Xe, and Rn) reactions: An example of fortuitous cancelling of relevant relativistic effects

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Autor(es):
Santiago, Regis T. [1] ; Haiduke, Roberto L. A. [1]
Número total de Autores: 2
Afiliação do(s) autor(es):
[1] Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol, CP 780, BR-13560970 Sao Carlos, SP - Brazil
Número total de Afiliações: 1
Tipo de documento: Artigo Científico
Fonte: Journal of Molecular Structure; v. 1249, FEB 5 2022.
Citações Web of Science: 0
Resumo

The relativistic effects on energetic quantities of the HNgF -> HF + Ng (Ng = Ar, Kr, Xe, and Rn) reactions were evaluated by means of advanced four-component calculations with high-level electron correlation treatment and adequate relativistic basis sets. The results indicate that the scalar relativistic corrections can provide classical barrier height increments of as much as 4.8% (1.9 kcal mol(-1)) for the reaction with the heaviest noble gas, radon, while the spin-orbit coupling is almost as important in this case, lowering the value by 3.8% (-1.5 kcal mol(-1)). Therefore, these two relevant relativistic corrections cancel almost completely. A similar picture is seen for the energy variation from the reactant (HRnF) to the products (HF + Rn), but the contribution signs are reversed now (-4.0 and 3.4 kcal mol(- 1)). A partial cancelling is also noticed for the HXeF -> HF + Xe reaction. Such pattern is surprising since scalar relativistic effects usually predominate by magnitude orders over the spin-orbit coupling. These conclusions are reflected in the changes observed in rate constant values. Finally, an alternative decomposition route catalyzed by HF is suggested for these HNgF compounds, which can shed some light on the controversies regarding their thermal stability. (C) 2021 Elsevier B.V. All rights reserved. (AU)

Processo FAPESP: 14/23714-1 - Cálculos relativísticos de estrutura eletrônica para avaliação de novos conjuntos de funções de base sem prolapso variacional
Beneficiário:Roberto Luiz Andrade Haiduke
Modalidade de apoio: Auxílio à Pesquisa - Regular