Quantum chemical study of atmospheric aggregates: HCl•HNO3•H2SO4

Abstract

HCl, HNO3 and H2SO4 are implicated in atmospheric processes in areas such as polar stratospheric clouds in the stratosphere. Ternary complexes of HCl, HNO3 and H2SO4 were investigated by ab initio calculations at B3LYP level of theory with aug-cc-pVTZ and aug-cc-pVQZ basis sets, taking into account basis set superposition error (BSSE). The results were assessed in terms of structures (five hexagonal cyclic structures and two quasi-pentagonal cyclic structures), inter-monomeric parameters (all ternary complexes built three hydrogen bonds), energetics (seven minima obtained), infrared harmonic vibrational frequencies (red shifting of complexes from monomers), and relative stability of complexes, which were favorable when the temperature decreases under stratospheric conditions, from 298 K to 188 K, and in concrete, at 210 K, 195 K and 188 K.

A DFT study on the mechanism of the sulfonic acid + alcohol esterification reaction

“…15 The resulting B3LYP/aug-cc-pVTZ method has provided good results on geometries and energetics of the hydrogen-bonded HCl-HNO 3 -H 2 SO 4 cluster. 16 Calculations were carried out by means of the Gaussian 09 soware package. 17 All stationary points were characterized by the correct number of imaginary frequencies (0 for minima, 1 for transition states, TS's).…”

“…The subsequent elimination step (through TS 14) leads to the formation of the hydrogen-bonded complex 15, which can nally dissociate to yield methyl benzenesulfonate (8) and oxonium cation (16).…”

“… 15 The resulting B3LYP/aug-cc-pVTZ method has provided good results on geometries and energetics of the hydrogen-bonded HCl–HNO 3 –H 2 SO 4 cluster. 16 …”

“…Basis set superposition error (BSSE) corrections were not considered in this work since those effects are typically negligible in studies using large basis sets (such as aug-cc-pVTZ). 16 Free energies at 25 °C in gas phase and methanol solution (by means of the IEF-PCM continuum model) for the most stable conformation of every structure were used for the discussion of the results throughout the paper. Relative Gibbs free energies for the calculated structures in gas phase (in parenthesis) and methanol solution (in square brackets), shown in figures, have been calculated by comparison with stabilities of the non-interacting starting reactants for every mechanistic pathway.…”

Facet shapes and thermo-stabilities of H2SO4•HNO3 hydrates involved in polar stratospheric clouds

“…Theoretical and density functional theory (DFT) calculations are previously performed like H 2 O species [25,26] [32][33][34][35][36], and H 2 SO 4 -HNO 3 -H 2 O/HCl ternary complexes [37][38][39] where their geometries, hydrogen bonds (HB), frequencies [40][41][42], and thermodynamic properties are accomplished.…”