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 this 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 $c_{\mathrm{p}}$, thermal expansion coefficient ${\alpha }_{\mathrm{p}}$, thermal conductivity λ, shear viscosity η and self-diffusion coefficient D. For the study, non-equilibrium molecular dynamics simulations were carried out. The fluid and the solid were modelled with the Lennard–Jones potential truncated and shifted at $r_{\mathrm{c}}^{\ast }=2.5\sigma$. The overall density of the fluid was $\overline{\rho }=0.8$. The overall temperature and 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 are generally below $15\mathrm{\%}$.

GRAPHICAL ABSTRACT

Keywords:

• Adsorption
• solid–fluid interface
• wetting
• anisotropy

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The project was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 252408385 – IRTG 2057 Physical Modeling for Virtual Manufacturing Systems and Processes as well as by the Federal Ministry of Education and Research (BMBF, Germany) – 01IH16008 – Task-based load balancing and auto-tuning in particle simulations (TaLPas). The simulations were carried out on the elwe at Regional University Computing Center Kaiserslautern (RHRK) under the grant TUKL-TLMV as well as on the HAZELHEN at the Supercomputing Centre Stuttgart (HLRS) under the grant 'Molecular Modelling of Hydrogen Bonding Fluids' (MMHBF2). This research was conducted under the auspices of the Boltzmann-Zuse Society for Computational Molecular Engineering (BZS).