Path-integral molecular dynamics simulations of small hydrated sulfuric acid clusters H2SO4•(H2O)n (n=1-6) on semiempirical PM6 potential surfaces
Path-integral molecular dynamics simulations of small hydrated sulfuric acid clusters H2SO4•(H2O)n (n=1-6) on semiempirical PM6 potential surfaces
复制标题
DOI：
10.1016/j.theochem.2009.01.022
复制
发表时间：
2009-05-15
影响因子：
--
通讯作者：
Tachikawa, Masanori
中科院分区：
文献类型：
--
作者：
Kakizaki, Akira;Motegi, Haruki;Tachikawa, Masanori
用新近发展起来的半经验PM6方法研究了水合硫酸团簇。在这个水平上优化了H_2SO_4中心点(H_2O)(N)(n=1-9)团簇的各种低能结构，并与以前的从头算和密度泛函理论进行了比较，以了解PM6方法在描述团簇中质子转移过程和氢键结构方面的适用性。尽管PM6方法似乎有点过分强调分叉氢键结构，但还是获得了较好的一致性。随后利用PM6势能及其梯度直接对H_2SO_4中心点(H_2O)(N)(n=1-6)团簇进行了量子路径积分分子动力学模拟。结果表明，酸解离几率随着团簇尺寸的增大而增加，质子解离团簇中以接触离子对结构为主。论证了核量子效应在团簇结构和质子转移过程中的重要性。(C)2009爱思唯尔B.V.保留所有权利。
A recently developed semiempirical PM6 method was applied to study small hydrated sulfuric acid clusters. Various low-energy structures of the H2SO4 center dot(H2O)(n) (n = 1-9) clusters were optimized at this level and then compared to previous ab initio and density-functional theory studies in order to understand the applicability of the PM6 method in describing proton-transfer processes as well as hydrogen-bonded Structures in the clusters. Although the PM6 method seems to somewhat overemphasize bifurcated hydrogen-bonded structures, moderately good agreement was obtained. Quantum path-integral molecular dynamics simulations for the H2SO4 center dot(H2O)(n) (n = 1-6) clusters were subsequently performed directly using PM6 potential energies and their gradients. It was found that the acid dissociation probability increases with an increase in the cluster size, as expected, and that so-called contact-ion-pair structures are dominant in the proton-dissociated clusters. The importance of nuclear quantum effects in the cluster structures and proton-transfer processes is demonstrated. (C) 2009 Elsevier B.V. All rights reserved.