Thermal, caloric and transport properties of the Lennard–Jones truncated and shifted fluid in the adsorbed layers at dispersive solid walls

Abstract

Fluid properties change when the fluid is adsorbed at a wall. The effect of the adsorption on the fluid properties was studied here by molecular simulation. There is much previous work in this field on fluids in nanochannels that are so small that the adsorbed layers on both walls interfere. In the present work the channel width was so large that the adsorbed layers did not interfere, such that information on the adsorbed layer on single walls was obtained and average values of thermodynamic properties of the fluid in that layer were determined.The studied fluid properties are: pressure p, density ρ, internal energy u, enthalpy h, isobaric heat capacity c p , thermal expansion coefficient α p , thermal conductivity λ, shear viscosity η, and self-diffusion coefficient D. For the study, non-equilibrium molecular dynamics simulations were carried out, i.e. gradients of the temperature and the velocity along different directions were applied. The fluid and the solid were modeled with the Lennard-Jones potential truncated and shifted at r * c = 2.5 σ. The overall density of the fluid was always ρ = 0.8 in the present simulations. The overall temperature as well as the solid-fluid interaction were varied. The corresponding bulk states are liquid or supercritical. The results for the fluid properties in the adsorbed layer were compared to the corresponding bulk values and the deviations were found to be generally below 15 %.

Molecular Dynamics Study of Wetting and Adsorption of Binary Mixtures of the Lennard-Jones Truncated and Shifted Fluid on a Planar Wall

“…In recent MD simulation studies, we have investigated the wetting and the adsorption of pure fluids on planar walls with the Lennard-Jones truncated and shifted (LJTS) potential with a cutoff radius of 2.5σ. , The same potential is used in the present work. The LJTS potential describes properties of simple fluids for a wide range of states and its properties are well known, − both for pure fluids and mixtures, and it has been used as a model fluid for many studies, for example, see refs − , − . The LJTS potential gives only crude descriptions of solids.…”

Understanding Electrolyte Filling of Lithium-Ion Battery Electrodes on the Pore Scale Using the Lattice Boltzmann Method

“…Thus, the wetting phase is highly attracted by the solid, increases the solid-fluid interface, and decreases fluid mobility. This is different for the nonwetting phase [23,53]. However, wettability and fluid connectivity are competing effects [53].…”

“…The multi-component Shan-Chen pseudopotential method (MCSC) has regularly been utilized to simulate multi-phase flows with LBM [19][20][21]. Similar to molecular dynamics simulations, where molecular interactions are modeled to study, e.g., wetting phenomena [22][23][24] or transport processes [25,26], it uses fluid-fluid and solid-fluid interaction forces to model interfacial tension and adhesion forces, respectively [20]. So far, LBM has been successfully applied to investigate water transport and hysteresis effects in catalyst or gas diffusion layers of polymer electrolyte membrane fuel cells [27][28][29][30][31][32][33].…”

Adsorption of Binary Mixtures of the Lennard-Jones Truncated and Shifted Fluid on Planar Walls

“…A solid LJTS wall was obtained by choosing ε s = 100 ε A , as in previous studies. ,,,, The solid particles were arranged in a face-centered cubic (fcc) lattice with the (100) surface exposed to the fluid; the lattice constant was a = 1.55 σ. All wall particles took part in the simulation; the crystal configuration remained unchanged in all simulations, due to the high energy parameter of the solid.…”

“…The interactions between all particles were described by the Lennard-Jones truncated and shifted (LJTS) potential with a cutoff radius of 2.5 σ. This potential is one of the simplest models for describing the properties of fluids for a wide range of states, and therefore, this or very similar fluids have been used extensively as model fluids for, for example, vapor–liquid equilibria, − interfaces between fluid phases, ,− transport properties, − and solid–fluid interactions. − Therefore, its properties are well known. ,,,− ,,,,,,,− Additionally, the LJTS fluid with a cutoff radius of 2.5 σ is described well by the Perturbed Truncated and Shifted (PeTS) equation of state (EOS) for pure fluids and for mixtures . By variation of the parameters of this simple potential, a wide variety of phenomena can be studied.…”