Theoretical Study of the Synergistic Effect of Hydroxymethanesulfonic Acid With Ammonia/Methylamine/Dimethylamine/Water in the Clustering

The study investigated the contribution of hydroxymethanesulfonic acid (HMSA) to the formation of new particles in the presence of atmospheric bases such as ammonia (A), methylamine (MA), dimethylamine (DMA) and water (W) by DLPNO-CCSD(T)/aug-cc-pVTZ//B3LYP-D3/aug-cc-pVTZ(aug-cc-pV(T+d)Z for sulfur) level. Clusters containing HMSA were found easily to form six− or eight−membered ring structures via SO—H⋯O (HMSA donor), O—H⋯O/N (W donor), N—H⋯O/N (A/MA/DMA donor), and C—H⋯O (MA/DMA donor) hydrogen bonds. Due to the synergistic interaction between X and Y molecules, the stability of HMSA−X−Y trimers is thermodynamically more favorable than HMSA−X dimers, and proton transfer was found to be exothermic and barrier−free in HMSA−X−Y trimers. Moreover, the stability of HMSA−X−Y trimers increased with higher alkalinity of X and Y, leading to decreased evaporation rates. The study highlights the significance of HMSA−containing trimers in nucleation processes for new particle formation, suggesting their potential role as nucleation centers in atmospheric conditions.