Bulk structural informations from density functionals for patchy particles

TL;DR

This study uses classical density functional theory to analyze the bulk structure of tetravalent patchy particles, comparing theoretical predictions with computer simulations, and evaluates the effectiveness of different functionals in capturing structural properties.

Contribution

It introduces a modified fundamental measure theory functional that accurately predicts bulk structures of patchy particles, highlighting its strengths and limitations compared to other functionals.

Findings

Modified functional yields accurate density profiles and radial distribution functions.

Functional performs well at high temperatures but less so at low temperatures with amorphous networks.

Segura et al.'s functional fails to capture key structural features.

Abstract

We investigate bulk structural properties of tetravalent associating particles within the framework of classical density functional theory, building upon Wertheim's thermodynamic perturbation theory. To this end, we calculate density profiles within an effective test-particle geometry and compare to radial distribution functions obtained from computer simulations. We demonstrate that a modified version of the functional proposed by Yu and Wu [J. Chem. Phys. 116, 7094 (2002)] based on fundamental measure theory for hard spheres produces accurate results, although the functional does not satisfy the exactly known low-density limit. However, at low temperatures where particles start to form an amorphous tetrahedral network, quantitative differences between simulations and theory emerge due to the absence of geometrical informations regarding the patch arrangement in the latter. Indeed, here we find that the theory fits better to simulations of the floating-bond model [J. Chem. Phys. 127, 174501 (2007)], which exhibits a weaker tetrahedral order due to more flexible bonds between particles. We also demonstrate that another common density functional approach by Segura \textit{et al.} [Mol. Phys. 90, 759 (1997)] fails to capture fundamental structural properties.