Ab-Initio Calculation of the Metal-Insulator Transition in Sodium rings and chains and in mixed Sodium-Lithium systems

TL;DR

This paper uses ab-initio quantum-chemical methods to investigate the metal-insulator transition in sodium and mixed sodium-lithium systems, analyzing effects of orbital inclusion, boundary conditions, and structural distortions.

Contribution

It introduces a detailed ab-initio approach to study the Mott transition and Peierls distortion in sodium and sodium-lithium systems, including effects of p-orbitals and boundary conditions.

Findings

Inclusion of p-orbitals significantly affects the MIT in lithium.

The character of the wavefunction changes with interatomic distance.

Bond alternation and Peierls distortion depend on system composition and conditions.

Abstract

We study how the Mott metal-insulator transition (MIT) is influenced when we deal with electrons with different angular momenta. For lithium we found an essential effect when we include $p$-orbitals in the description of the Hilbert space. We apply quantum-chemical methods to sodium rings and chains in order to investigate the analogue of a MIT, and how it is influenced by periodic and open boundaries. By changing the interatomic distance we analyse the character of the many-body wavefunction and the charge gap. In the second part we mimic a behaviour found in the ionic Hubbard model, where a transition from a band to a Mott insulator occurs. For that purpose we perform calculations for mixed sodium-lithium rings. In addition, we examine the question of bond alternation for the pure sodium system and the mixed sodium-lithium system, in order to determine under which conditions a Peierls distortion occurs.