Influence of confinement on thermodiffusion

Rachid Hannaoui (1) , Guillaume Galliero (1) , Hai Hoang (1) , Christian Boned (1)

1 LFCR - Laboratoire des Fluides Complexes et leurs Réservoirs

This work focuses on a possible influence of a nanoporous medium on the thermodiffusion of a fluid "isotopic" mixture. To do so, we performed molecular dynamics simulations of confined Lennard- Jones binary equimolar mixtures using grand-canonical like and non-equilibrium approaches in suband super-critical conditions. The study was conducted in atomistic slit pore of three adsorbent natures for various widths (from 5 to 35 times the size of a molecule). The simulation results indicate that for all thermodynamic conditions and whatever the pore characteristics, the confinement has a negligible effect on the thermal diffusion factor/Soret coefficient. However, when considered separately, the mass diffusion and thermodiffusion coefficients have been found to be largely influenced by the pore characteristics. These two coefficients decrease noticeably when adsorption is stronger and pore width smaller, a behavior that is consistent with a simple hydrodynamic explanation.

Mots clés: Equimolar mixtures; Molecular dynamics simulations; Non equilibrium; Pore characteristics; Thermal diffusion factors; Thermodiffusion; Thermodiffusion coefficients; Thermodynamic conditions Engineering controlled terms: Binary mixtures; Molecular dynamics Engineering main heading: Thermal diffusion in liquids

Domaines: Chimie-Physique [physics.chem-ph]

Rachid Hannaoui, Guillaume Galliero, Hai Hoang, Christian Boned. Influence of confinement on thermodiffusion. Journal of Chemical Physics, 2013, 139 (11), pp.Article number 114704. ⟨10.1063/1.4821128⟩. ⟨hal-00879672⟩