Effective Polarisability Models

TL;DR

This paper compares various models for calculating the effective polarisability of small particles in media, incorporating simulation data to improve understanding of van der Waals and Casimir-Polder interactions.

Contribution

It introduces a unified approach combining different approximation models with simulation data for more accurate effective polarisability calculations.

Findings

Effective polarisabilities at Matsubara frequencies are computed for different models.

Simulation-derived radii improve the accuracy of polarisability estimates.

The models are applied to van der Waals and Casimir-Polder interactions in water.

Abstract

Theories for the effective polarisability of a small particle in a medium are presented using different levels of approximation: we consider the virtual cavity, real cavity and the hard-sphere models as well as a continuous interpolation of the latter two. We present the respective hard-sphere and cavity radii as obtained from density-functional simulations as well as the resulting effective polarisabilities at discrete Matsubara frequencies. This enables us to account for macroscopic media in van der Waals interactions between molecules in water and their Casimir-Polder interaction with an interface.