Interactions of sulfuric acid with common atmospheric bases and organic acids: Thermodynamics and implications to new particle formation.

Interactions of the three common atmospheric bases, dimethylamine ((CH)NH), methylamine (CHNH), ammonia (NH), all considered to be efficient stabilizers of binary clusters in the Earth's atmosphere, with HSO, the key atmospheric precursor, and 14 common atmospheric organic acids (COAs) (formic, acetic, oxalic, malonic, succinic, glutaric acid, adipic, benzoic, phenylacetic, pyruvic, maleic acid, malic, tartaric and pinonic acids) have been studied using the density functional theory (DFT) and composite high-accuracy G3MP2 method. The thermodynamic stability of mixed (COA)(HSO), (COA)(B1), (COA)(B2) and (COA)(B3) dimers and (COA)(HSO)(B1), (COA)(HSO)(B2) and (COA)(HSO)(B3) trimers, where B1, B2 and B3 refer to (CH)NH, CHNH and NH, respectively, have been investigated and their impacts on the thermodynamic stability of clusters containing HSO have been studied. Our investigation shows that interactions of HSO with COA, (CH)NH, CHNH and NH lead to the formation of more stable mixed dimers and trimers than (HSO) and (HSO)(base), respectively, and emphasize the importance of common organic species for early stages of atmospheric nucleation. We also show that although amines are generally confirmed to be more active than NH as stabilizers of binary clusters, in some cases mixed trimers containing NH are more stable thermodynamically than those containing CHNH. This study indicates an important role of COA, which coexist and interact with that HSO and common atmospheric bases in the Earth atmosphere, in formation of stable pre-nucleation clusters and suggests that the impacts of COA on new particle formation (NPF) should be studied in further details.