Methanesulfonate (MSA?), found in substantial concentrations in the atmosphere, is expected to enhance aerosol nucleation and the growth of nanoparticles, but the details of methanesulfonate clusters are poorly understood. In this study, MSA? was chosen along with ammonia (NH3) or three common amines and water (H2O) to discuss the roles of ternary homogeneous nucleation and ion-induced nucleation in aerosol formation. We studied the structural characteristics and thermodynamics of the clusters using density functional theory at the PW91PW91/6-311++G(3df,3pd) level. The analysis of noncovalent interactions predicts that the amines can form more stable clusters with MSA? than NH3, in agreement with the results from structures and thermodynamics; however, the enhancement in stability for amines is not large enough to overcome the difference in the concentrations of NH3 and amines under typical atmospheric conditions. In addition, the favorable free energies of formation for the (MSA?)(NH3/amines)(H2O)n (n = 0–3) clusters at 298.15 K show that MSA? could contribute to the aerosol nucleation process with binding NH3/amines and H2O up to n = 3. There are strong temperature and humidity dependences for the formation of complexes; higher humidity and temperature promote the formation of larger hydrates. Finally, for the (MSA?)(NH3/amines)(H2O)n clusters, the evaporation rates were determined to further investigate the atmospheric implications.
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机译：甲烷磺酸盐（MSA ？ ）在大气中的浓度很高，有望增强气溶胶成核作用和纳米颗粒的生长，但是人们对甲烷磺酸盐簇的细节了解甚少。在这项研究中，选择了MSA ？ 以及氨水（NH 3 ）或三种常见的胺和水（ H 2 O）讨论三元均相成核和离子诱导成核在气溶胶形成中的作用。我们使用密度泛函理论在PW91PW91 / 6-311 ++ G（3df，3pd）水平上研究了团簇的结构特征和热力学。非共价相互作用的分析预测，与NH 3 相比，胺与MSA ？ 可以形成更稳定的簇。与结构和热力学的结果一致;然而，胺的稳定性提高幅度不足以克服典型大气条件下NH 3 和胺的浓度差异。此外，（MSA ？ ）（NH 3 / smalls /胺）的有利的形成自由能（ H 2 O） n （ n = 0–3）在298.15 K处的簇表明，MSA ？ 可以通过结合NH 3 /胺和H 2 O最多达到 n =3。络合物的形成对温度和湿度有很强的依赖性。较高的湿度和温度会促进形成较大的水合物。最后，对于（MSA ？ ）（NH 3 /胺）（H 2 O） n 团簇，确定了蒸发速率以进一步研究大气影响。
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