title: Ab initio metadynamics study on hydronium ion dynamics at acid-functionalized interfaces: effect of surface group density.
abstract: 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.
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A1S6. meikerl@sfu.ca.
authors.forename: Swati
authors.initials: S
authors.lastname: Vartak
authors.forename: Anatoly
authors.initials: A
authors.lastname: Golovnev
authors.forename: Ata
authors.initials: A
authors.lastname: Roudgar
authors.forename: Michael
authors.initials: M
authors.lastname: Eikerling
mesh_terms: D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D009861:Onium Compounds / Q000737:chemistry*; D011522:Protons; D013816:Thermodynamics
chemical_list: D009861:Onium Compounds; D011522:Protons; C027727:hydronium ion