Influence of Liquid Structure on Fickian Diffusion in Binary Mixtures of n-Hexane and Carbon Dioxide Probed by Dynamic Light Scattering, Raman Spectroscopy, and Molecular Dynamics Simulations

• DOI: 10.1021/acs.jpcb.8b03568
• Publication Date: 2018-06-11T19:41:27Z
• Authors: Tobias Klein; Wenchang Wu; Michael H. Rausch; Cédric Giraudet; Thomas M. Koller; Andreas P. Fröba
• Keywords: Hexane; Dynamics

This study contributes to a fundamental understanding of how the liquid structure in model system consisting weakly associative n-hexane (n-C6H14) and carbon dioxide (CO2) influences Fickian diffusion process. For this, benefits light scattering experiments molecular dynamics (MD) simulations at macroscopic thermodynamic equilibrium were combined synergistically. Our reference diffusivities measured by dynamic (DLS) revealed an unusual trend with increasing CO2 mole fractions up about 70 mol %, which agrees our simulation results. The impacts on analyzed MD simulations, where kinetic contributions related Maxwell–Stefan (MS) diffusivity structural quantified factor studied separately. Both MS indicate deceleration compared ideal mixture behavior. Computed radial distribution functions as well significant blue-shift CH stretching modes n-C6H14 identified Raman spectroscopy show that slowing down is caused organization binary mixtures over broad concentration range form self-associated domains. These networks start close infinite dilution limits seem have their largest extent solute–solvent transition point % CO2. current results not only improve general mass liquids but also serve develop sound prediction models for Fick diffusivities.