Ab-Initio Calculation of the Metal-Insulator Transition in Lithium rings

TL;DR

This paper uses ab-initio quantum-chemical methods to analyze the Mott metal-insulator transition in lithium rings, focusing on the effects of orbital degeneracy and structural distortions.

Contribution

It provides a detailed ab-initio investigation of the metal-insulator transition in lithium rings, highlighting the role of $s-p$ orbital quasi-degeneracy and Peierls distortion conditions.

Findings

Charge gap shows a minimum at a specific lattice constant.

Static electric dipole polarizability peaks at the transition point.

Peierls distortion occurs under certain bond alternation conditions.

Abstract

We study how the Mott metal-insulator transition (MIT) is affected when we have to deal with electrons with different angular momentum quantum numbers. For that purpose we apply ab-initio quantum-chemical methods to lithium rings in order to investigate the analogue of a MIT. By changing the interatomic distance we analyse the character of the many-body wavefunction and discuss the importance of the $s-p$ orbital quasi-degeneracy within the metallic regime. The charge gap (ionization potential minus electron affinity) shows a minimum and the static electric dipole polarizability has a pronounced maximum at a lattice constant where the character of the wavefunction changes from significant $p$ to essentially $s$-type. In addition, we examine rings with bond alternation in order to answer the question under which conditions a Peierls distortion occurs.