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Item type:Publication, Access status: without files , Viscosities of inhomogeneous systems from generalized entropy scaling(American Institute of Physics (AIP), 2024-04-01); ; ; ; This study extends entropy scaling to inhomogeneous fluids by using the classical density functional theory together with a new viscosity reference that takes into account the influence of solid-fluid interactions on the fluid viscosity. The density functional theory uses a Helmholtz energy functional based on the perturbed-chain statistical associating fluid theory; the local residual entropy per particle is determined from the temperature derivative of the Helmholtz energy functional in combination with an appropriate weighted density profile. The weighted density calculation requires a single transferable parameter, which is adjusted to a reference molecular dynamics simulation. In particular, local viscosity values for fluids under nanoconfinement near solid-fluid interfaces are predicted using the same entropy scaling parameters as for homogeneous fluids. We validate the model by comparing viscosity and velocity profiles with results from non-equilibrium molecular dynamics simulations of a Couette flow in a slit pore. Good agreement is found between the entropy scaling model and the non-equilibrium molecular dynamics results for both the viscosity and velocity profiles of the Lennard-Jones truncated and shifted fluid. The proposed model extrapolates well to systems with different temperatures, fluid densities, and shear forces as well as to systems with different wetting behaviors. These results demonstrate that entropy scaling can be generalized to inhomogeneous fluids using an appropriate combination of residual entropy profile and viscosity reference.Publicationtype: Journal Article16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Predicting the relative static permittivity: a group contribution method based on perturbation theory(American Chemical Society (ACS), 2024-02-08); ; ; Esper, TimmThe computer-aided design of (bio)chemical processes requires models that predict thermodynamic properties with as little experimental effort as possible. For the important class of electrolyte systems, the relative static permittivity of the solvent is an important thermodynamic property that depends on the temperature, pressure, composition, and molecular structure of the solvent. This work presents a broadly applicable model for the temperature-dependent relative static permittivity of pure and mixed solvents based on perturbation theory, including a group contribution method. For this purpose, we extend our previous model for polar substances to nonpolar substances. The developed model is parametrized for 785 substances, where permittivity and density data are available in the Dortmund Data Bank and the ThermoML database. Subsequently, a group contribution method is developed to predict the permittivity parameters from the molecular structure. With a mean absolute deviation of 0.2 averaged over all 785 substances, the parametrized model accurately correlates the relative static permittivity over a wide range of permittivities and temperatures. Moreover, the group contribution method achieves a mean absolute deviation of 0.6 for the substances in the training set. A leave-one-out cross-validation shows that the group contribution method accurately predicts substances not included in the training set.Publicationtype: Journal ArticleScopus© Citations 1 38 89