arXiv subjects

Melih Gül

Publications and source records attributed to Melih Gül.

4 recordsLinked to original sources

arXiv2026

Effective one-body interactions due to the presence of a liquid-vapor interface

In this study we investigate the behavior of additive binary square-well mixtures within the framework of classical density functional theory. By leveraging on the geometrical structure of the square-well interaction, we propose a novel form of the perturbation theory contribution to the density functional in terms of weighted densities, inspired by fundamental measure theory. We apply this functional in order to study the effective one-body interaction due to the liquid-vapor interface of the solvent acting on a dilute component of dissolved nano particles. The effective one-body interaction attracts the nano particles strongly to the interface. We show that this effective interaction potential can be calculated either from the density profiles of the full mixture, at low but non-vanishing concentrations of the nano particles, or by employing the Widom insertion theorem in the dilute limit of vanishing density of nano particles. Both routes display excellent agreement.

cond-mat.soft↗

arXiv2026

Using test particle sum rules to improve approximations in classical DFT : White-Bear and White-Bear mark II versions of the Lutsko Functional

In a recent paper [M. Gül et al., Phys. Rev. E, 110 (6), 064115] we showed that test particle sum rules, which address the excess chemical potential and isothermal compressibility, could be used to develop new and accurate classical density functionals for hard-sphere (HS) fluids. Here we extend our approach to the construction of HS functionals building upon the state of art White-Bear (WB) and White-Bear mark II functionals. Employing the same test-particle sum rules we determine the two free parameters in the Lutsko [James F. Lutsko, Phys. Rev. E, 102, 062137] formulation of fundamental measure theory (FMT) by minimizing the relative errors between different routes to the two thermodynamic quantities. The resulting optimized Lutsko WB functionals, especially Lutsko WB mark II, are generally more accurate and consistent than those obtained in earlier treatments.

cond-mat.soft↗

arXiv2025

Classical density functional theory for nanoparticle-laden droplets

Droplets of a pure fluid, such as water, in an open container surrounded by gas, are thermodynamically unstable and evaporate quickly. In a recent paper [Archer et al. J. Chem. Phys. {\bf 159}, 194403 (2023)] we employed lattice density functional theory (DFT) to demonstrate that nanoparticles or solutes dissolved in a liquid droplet can make it thermodynamically stable against evaporation. In this study, we extend our model by using continuum DFT, which allows for a more accurate description of the fluid and nanoparticle density distributions within the droplet and enables us to consider size ratios between nanoparticles and solvent particles up to 10:1. While the results of the continuum DFT agrees well with those of our earlier lattice DFT findings, our approach here allows us to refine our understanding of the stability and structure of nanoparticle laden droplets. This is particularly relevant in light of the recent global COVID-19 pandemic, which has underscored the critical role of aerosol particles in virus transmission. Understanding the stability and lifetime of these viron-laden aerosols is crucial for assessing their impact on airborne disease spread.

cond-mat.soft↗

arXiv2024

Using test particle sum rules to construct accurate functionals in classical Density Functional Theory

Fundamental Measure Theory (FMT) is a successful and versatile approach for describing the properties of the hard-sphere fluid and hard-sphere mixtures within the framework of classical density functional theory (DFT). Lutsko [Phys. Rev. E 102, 062137 (2020)] introduced a version of FMT containing two free parameters, to be fixed by additional physical constraints. Whereas Lutsko focused on the stability of crystalline phases, we introduce and employ two statistical mechanical sum rules pertinent for the fluid phase, that are not automatically satisfied by FMT. By minimizing the relative deviation between different routes to calculate the excess chemical potential and the isothermal compressibility we determine the two free parameters of the theory. Our results indicate that requiring consistency with these sum rules can improve the quality of predictions of FMT for properties of the hard-sphere fluid phase. We suggest that employing these (test particle) sum rules, which apply for any interparticle pair-potential, might provide a means of testing the performance and accuracy of general DFT approximations.

cond-mat.soft↗