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

TL;DR

This paper enhances classical density functionals for hard-sphere fluids by using test particle sum rules to optimize the Lutsko functional versions of the White-Bear models, improving accuracy and consistency.

Contribution

It introduces a method to optimize Lutsko-based White-Bear functionals using test particle sum rules, leading to more accurate classical density functionals.

Findings

Lutsko WB mark II functional shows improved accuracy.

Optimization reduces errors between thermodynamic routes.

Enhanced functionals are more consistent with physical data.

Abstract

In a recent paper [M. G\"ul 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.