Study on Atmospheric Physicochemical Characterization of 2-Methylglyceric Acid-Water Clusters
New particle formation is a major source of atmospheric aerosols,and critical nucleation is the starting point.Cur-rently,information on nucleation species and mechanisms at the molecular level is incomplete.2-Methylglycerol acid(MGA)and water(H2O),as potential nucleation precursors,may contribute to atmospheric new particle formation.Therefore,the geometrical structure,thermodynamic properties,and relative occupancy of isomers of MGA-H2O clusters were explored based on density-functional theory(DFT).The results show:(MGA)(H2O)n(n=1～4)clusters all have stable structures,but only the formation of(MGA)(H2O)2 and(MGA)(H2O)3 clusters can proceed spontaneously,thus predicting the temperature dependence of the relative proportion of isomers in(MGA)(H2O)2 and(MGA)(H2O)3 cluster isomers in the atmosphere;the most stable structures(global minimum)of(MGA)(H2O)2 and(MGA)(H2O)3 clusters dominate at low temperatures;the percentages of other low-energy isomers increase rapidly with increasing temperature.In addition,H2O prefers to bind to MGA in the form of cluster(H2O)n.Overall,the MGA-H2O system is able to contribute to atmospheric new particle formation in the form of dihy-drate(MGA)(H2O)2 and trihydrate(MGA)(H2O)3.
atmospheric aerosolsclustersnew particle formationdensity functional theory
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