Orientational dependence of the van der Waals interactions for finite-sized particles

TL;DR

This paper develops an effective theory to describe how the orientation and finite size of particles influence van der Waals interactions, extending beyond the point dipole approximation to include anisotropy and higher multipole effects.

Contribution

It introduces a method using spatially spread out polarizability distributions to account for finite size and anisotropy in van der Waals interactions, improving theoretical accuracy.

Findings

Effective theory for anisotropic, finite-sized particles

Inclusion of higher multipole effects in van der Waals potential

Enhanced understanding of distance-dependent interactions

Abstract

Van der Waals forces as interactions between neutral and polarisable particles act at small distances between two objects. Their theoretical origin lies in the electromagnetic interaction between induced dipole moments caused by the vacuum fluctuations of the ground-state electromagnetic field. The resulting theory well describes the experimental situation in the limit of the point dipole assumption. At smaller distances, where the finite size of the particles has to be taken into account, this description fails and has to be corrected by higher orders of the multipole expansion, such as quadrupole moments and so on. With respect to the complexity of the spatial properties of the particles this task requires a considerable effort. In order to describe the van der Waals interaction between such particles, we apply the established method of a spatially spread out polarisability distribution to approximate the higher orders of the multipole expansion. We hence construct an effective theory for effects from anisotropy and finite size on the van der Waals potential.