The driving effects of common atmospheric molecules for formation of clusters: the case of sulfuric acid, formic acid, hydrochloric acid, ammonia, and dimethylamine

Abstract

One of the main sources of uncertainty for understanding global warming is understanding the formation of larger secondary aerosols. The beginning stages start with the formation of prenucleation complexes from...

The driving effects of common atmospheric molecules for formation of clusters: the case of sulfuric acid, nitric acid, hydrochloric acid, ammonia, and dimethylamine

“…This is a rough estimate based on the three orders of magnitude decrease in concentration of water, and we used this approximation since experimental concentrations of these monomers in the upper troposphere are difficult to measure. These results were combined with results from the previously studied (SA)(FA)(NA)(A)(DMA)(W) 0-3 and (SA)(FA)(HCl)(A)(DMA)(W) 0-3 clusters, 72,86 allowing for a comparison of the different combinations of three different acids with the two different bases. We note that there are several limitations to our methodology.…”

“…72,86 We have not included the two acid dimers containing HCl, [(SA)(HCl)(W) 0-3 , (NA)(HCl)(W) 0-3 , and (FA)(HCl)(W) 0-3 ] as previous results have shown these clusters are not atmospherically signicant due to the lack of hydrogen bonding sites and bases present for deprotonation. 72,86 The (SA)(NA)(HCl) trimer structure is included in the ESI † along with the energetics for the hydration of all the three acid clusters (Fig. S6 and Table T6 †).…”

“…72 Most recently, we swapped NA for hydrochloric acid (HCl), and explored all possible combinations of SA, FA, HCl, A, DMA, and up to three W to probe the effects of this swap of one strong acid for another. 86 This rst detailed study of HCl interacting with two other acids and two bases revealed that NA forms stronger interactions in dry clusters than HCl, but sometimes as the clusters grow larger and are hydrated the sequential Gibbs free energies of clusters containing HCl become more favorable than those for NA. 86 Overall this previous work adds to the body of evidence that reveals that hydrogen bond topology and the detailed structural interactions within a prenucleation cluster are as important as conventional ideas such as acid/base strength.…”

“…86 This rst detailed study of HCl interacting with two other acids and two bases revealed that NA forms stronger interactions in dry clusters than HCl, but sometimes as the clusters grow larger and are hydrated the sequential Gibbs free energies of clusters containing HCl become more favorable than those for NA. 86 Overall this previous work adds to the body of evidence that reveals that hydrogen bond topology and the detailed structural interactions within a prenucleation cluster are as important as conventional ideas such as acid/base strength. Prenucleation clusters, held together by hydrogen bonding and other van der Waals forces, have free energies determined by the subtle interactions between enthalpy and entropy, which depend on the molecular structure of the complex.…”

“…14 Our recent examination of prenucleation complexes which contain formic acid, a weaker acid compared to sulfuric acid, nitric acid, and hydrochloric acid, in clusters of unequal amounts of acids and bases, reveal that the detailed hydrogen bonding topology of a particular cluster is sometimes more important than traditional acid/base strength. 65,67,72,86 In our previous work we have simulated how sulfuric acid (SA), formic acid (FA), ammonia (A), and water (W), form prenucleation complexes and discovered that FA is as effective as A at forming clusters with SA. 65 We have also computed all the interactions between SA, A, and the amino acids glycine and serine, and found that the amino acids and A are practically interchangeable, and there is no easy way to predict which of the three molecules are protonated when SA loses its proton to one of those species.…”