Classical double-layer atoms: artificial molecules

TL;DR

This paper investigates the structural and vibrational properties of two classical particles confined in harmonic wells and interacting via Coulomb repulsion, revealing multiple phase transitions as the inter-particle distance varies.

Contribution

It provides a detailed analysis of the ground state configurations and eigenmodes of classical double-layer atoms, identifying various first and second order structural transitions.

Findings

Identification of multiple structural transitions as a function of inter-atomic distance

Discontinuous changes in particle positions and energy derivatives at transition points

Occurrence of mode softening indicating second order transitions

Abstract

The groundstate configuration and the eigenmodes of two parallel two-dimensional classical atoms are obtained as function of the inter-atomic distance (d). The classical particles are confined by identical harmonic wells and repel each other through a Coulomb potential. As function of d we find several structural transitions which are of first or second order. For first (second) order transitions the first (second) derivative of the energy with respect to d is discontinuous, the radial position of the particles changes discontinuously (continuously) and the frequency of the eigenmodes exhibit a jump (one mode becomes soft, i.e. its frequency becomes zero).