A systematic ab initio optimization of monohydrates of HCl•HNO3•H2SO4 aggregates.

Abstract Hydrates of HCl, HNO 3 and H 2 SO 4 involved in polar stratospheric clouds capture the attention of researchers due to the mixtures composed with them. The molecular aggregates generated with these strong acids show different behaviors, geometries and nucleation reactions at atmospheric temperatures. Here is presented a systematic ab initio optimization study of monohydrates of HCl•HNO 3 •H 2 SO 4 using the Density Functional Theory, by means of geometry optimizations carried out with B3LYP hybrid method and aug-cc-pVTZ basis set, a high level of theory, within Gaussian 09 program. This systematic optimization procedure consists to situate systematically the H 2 O molecule around the cluster in study, on the favorable positions to develop higher quantity of hydrogen bonds as possible, in order to obtain major quantity of different electronic structures of these monohydrates. Applying this systematic optimization methodology over previously optimized complexes of HCl, HNO 3 and H 2 SO 4 , the present theoretical approach provides thirty-two different optimized electronic structures of monohydrates that were yielded from seven initial groups of (HCl•HNO 3 •H 2 SO 4)-complex, placing the H 2 O in eight positions around them. Moreover, their Infrared spectra have been predicted for all (HCl•HNO 3 •H 2 SO 4)-monohydrates achieved. Likewise, It is shown the outcomes of the electronic energies, relative Gibbs free energies, Infrared spectra, the wavenumbers of hydrogen bonds, inter-monomeric parameters, electronic structures of (HCl•HNO 3 •H 2 SO 4)-monohydrates. These monohydrates could be considered precursors of the atmospheric heterogeneous nucleation reactions. These results can be useful to experimentalists of Catalysis, Astrophysics, Corrosion of metals and ceramics, aromatic compounds reactions, even environmental pollution and industrial smog. Graphical abstract Heterogeneous atmospheric reactions implicated in ozone depletion remain unknown. The stratospheric nucleation reactions are an aim for both experimental and theoretical researchers, mainly the heterogeneous nucleation reactions where the HCl, HNO 3 and H 2 SO 4 molecules are involved. The ab initio electronic structure optimizations for (HCl•HNO 3 •H 2 SO 4)-monohydrates have been carried out applying an ab initio systematic optimization procedure. The different H 2 O molecule positions around of each one of the seven (HCl•HNO 3 •H 2 SO 4)-complexes provide accurately fifty-six optimized (CNS-K+1W I)-monohydrates. All electronic structures optimizations have carried out by means of DFT method alongside the aug-cc-pVTZ of Dunning's basis set. The geometries optimizations offer the global minimum and relative minima structures for each one of (CNS-K+1W I)-monohydrates optimized. Thirty-two different electronic structures of (HCl•HNO 3 •H 2 SO 4)-monohydrates have been achieved from fifty-six optimized monohydrates geometries. Besides, the hydrogen bond interactions have been predicted in the infrared spectra for all (CNS-K+1W I)-monohydrates, whose outcomes are in consonance with experimental data. As well as, the relative electronic and relative Gibbs free energies, the inter-monomeric hydrogen bonds, and this inter-, and intra-monomeric parameters have been obtained. This theoretical approach can be useful to experimentalist in fields like Atmospheric Chemistry, Climate Change, Environmental Pollution, Astrophysics, and Catalysis, Corrosion of metals and ceramics, and reactions of aromatic compounds. This systematic ab initio optimization method guarantees to reach all different electronic structures for any molecular system optimized. IR spectra of each global minima for each one of (HCl•HNO 3 •H 2 SO 4)-monohydrates or (CNS- K +1W i). Image 1 Highlights • Systematic ab initio optimization procedure to achieve electronic structures with DFT method. • Ab initio optimizations of (HCl·HNO 3 ·H 2 SO 4)-monohydrates geometries. • Thirty-two different electronic structures of (CNS-K+1Wi)-monohydrates optimized. • Infrared spectra and inter-monomeric hydrogen bonds for each (CNS-K+1Wi)-monohydrate. • Geometries, hexagonal ring, electronic and Gibbs free energies of each monohydrate. [ABSTRACT FROM AUTHOR]