Vartak Swati, Golovnev Anatoly, Roudgar Ata, Eikerling Michael
Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A1S6.
Phys Chem Chem Phys. 2014 Nov 21;16(43):24099-107. doi: 10.1039/c4cp02937b. Epub 2014 Oct 7.
This article presents an ab initio metadynamics study of elementary hydronium ion transitions at dense arrays of surface groups with sulfonic acid head groups. Calculations simulate minimally hydrated conditions of the interfacial ionic system. The specific focus is on the influence of the surface group density on hydronium ion transport. Results reveal a high sensitivity of the activation free energy of hydronium translocations to the surface group density. A spontaneous concerted transition with low activation barrier is found at a surface group separation of 6.8 Å. When hydroniums translocate concertedly, the activation barrier of the transition drops by more than a factor of two to the value of 0.25 eV. An approach is presented to determine interaction constants of hydronium ions and anionic surface groups as well as the surface group flexibility from the analysis of frequency spectra. These properties are discussed in the context of a recently developed soliton theory of interfacial proton transport.
本文介绍了对具有磺酸头基的表面基团密集阵列处初级水合氢离子跃迁的从头算元动力学研究。计算模拟了界面离子系统的最低水合条件。具体重点在于表面基团密度对水合氢离子传输的影响。结果表明，水合氢离子迁移的活化自由能对表面基团密度高度敏感。在表面基团间距为6.8 Å时发现了具有低活化能垒的自发协同跃迁。当水合氢离子协同迁移时，跃迁的活化能垒下降超过两倍，降至0.25 eV的值。提出了一种通过频谱分析来确定水合氢离子与阴离子表面基团的相互作用常数以及表面基团柔韧性的方法。在最近发展的界面质子传输孤子理论的背景下讨论了这些性质。
