Ionic mixtures in two dimensions: from crystals to chain and dipole gases

TL;DR

This paper investigates the ground states of two-dimensional ionic mixtures, revealing a sequence of stable crystal and gas phases, and predicts new phases for experimental detection in granular and colloidal systems.

Contribution

It introduces a comprehensive analysis of phase structures in 2D ionic mixtures, including new predicted phases not previously observed.

Findings

Confirmed experimentally observed square crystal structure.

Identified stable triangular, rhombic, and chain phases.

Predicted new phases for experimental validation.

Abstract

The ground state of a two-dimensional ionic mixture composed of oppositely charged spheres is determined as a function of the size asymmetry by using a penalty method. The cascade of stable structures includes square, triangular and rhombic crystals as well as a dipolar pair gas and a gas of one-dimensional crystalline chains. Thereby we confirm the square structure, found experimentally on charged granulates, and predict new phases detectable in experiments on granular and colloidal matter.