Wigner crystals for a planar, equimolar binary mixture of classical, charged particles

TL;DR

This study explores the ground state configurations of a binary mixture of classical charged particles on a plane, revealing complex ordered structures and phase separation phenomena across various charge ratios.

Contribution

It introduces an efficient computational approach combining Ewald summation and evolutionary algorithms to identify novel and complex ground state arrangements in charged particle mixtures.

Findings

Identified six non-trivial ground states with structural complexity.

Discovered phase separation with hexagonal arrangements for specific charge ratios.

Revealed unexpected structural phenomena in charged particle mixtures.

Abstract

We have investigated the ground state configurations of an equimolar, binary mixture of classical charged particles (with nominal charges $Q_1$ and $Q_2$) that condensate on a neutralizing plane. Using efficient Ewald summation techniques for the calculation of the ground state energies, we have identified the energetically most favourable ordered particle arrangements with the help of a highly reliable optimization tool based on ideas of evolutionary algorithms. Over a large range of charge ratios, $q = Q_2 / Q_1$, we identify six non-trivial ground states, some of which show a remarkable and unexpected structural complexity. For $0.59 \lesssim q < 1$ the system undergoes a phase separation where the two charge species populate in a hexagonal arrangement spatially separated areas.