Kangas Pinja, Hänninen Vesa, Halonen Lauri
Department of Chemistry, University of Helsinki, P.O. Box 55 (A.I. Virtasen aukio 1), FIN-00014 Helsinki, Finland.
J Phys Chem A. 2020 Mar 12;124(10):1922-1928. doi: 10.1021/acs.jpca.9b11954. Epub 2020 Mar 3.
Ab initio molecular dynamics (AIMD) calculations have been performed to investigate the role of dynamical and steric effects in formic acid (FA) or HO-catalyzed gas phase hydrolysis of SO to form sulfuric acid. This was done by colliding FA or HO with the SO-HO complex and the water dimer with the SO molecule and analyzing the outcomes of 230 AIMD trajectories. Our calculations show that, within simulation times used, sulfuric acid is formed in 5% of FA collisions but is not produced when HO collides with the SO-HO complex or when the water dimer collides with the SO molecule. We also find that FA collisions have about 2 times higher probability to form the prereactive complex than HO collisions. Moreover, our simulations show that the SO-HO-FA prereactive complex is more stable in time than the SO-HO-HO prereactive complex. These findings indicate that the FA-catalyzed mechanism is favored over the HO one when looking from the steric and dynamic effect point of view. Additionally, AIMD simulations starting from the optimized structure of the SO-HO-FA prereactive complex have been computed to qualitatively estimate the rate of the sulfuric acid formation. Collisional energy has been observed to promote sulfuric acid formation more effectively than thermal excitation.
已进行从头算分子动力学（AIMD）计算，以研究动力学和空间效应在甲酸（FA）或羟基（HO）催化的二氧化硫（SO）气相水解生成硫酸过程中的作用。具体做法是使FA或HO与SO - HO络合物以及水二聚体与SO分子发生碰撞，并分析230条AIMD轨迹的结果。我们的计算表明，在所使用的模拟时间内，5%的FA碰撞会生成硫酸，但HO与SO - HO络合物碰撞或水二聚体与SO分子碰撞时不会产生硫酸。我们还发现，FA碰撞形成预反应络合物的概率比HO碰撞高约2倍。此外，我们的模拟表明，SO - HO - FA预反应络合物在时间上比SO - HO - HO预反应络合物更稳定。这些发现表明，从空间和动力学效应的角度来看，FA催化的机制比HO催化的机制更有利。此外，已从SO - HO - FA预反应络合物的优化结构出发进行AIMD模拟，以定性估计硫酸形成的速率。已观察到碰撞能量比热激发更有效地促进硫酸的形成。
