# A configuration interaction approach to solve the Anderson impurity model; applications to elemental Ce

## TL;DR

This paper introduces an efficient configuration interaction solver for the dynamical mean field theory, enabling accurate and accessible calculations of strongly correlated materials like elemental cerium on standard computing hardware.

## Contribution

It presents a novel, efficient CI-based solver for DMFT that outperforms traditional methods and is accessible on common computers, demonstrated on elemental cerium phases.

## Key findings

- The solver accurately captures the electronic structure of cerium phases.
- It reveals the evolution from localized to itinerant 4f electrons in cerium.
- The transition between phases resembles a Mott transition, with a Kondo singlet in the alpha phase.

## Abstract

Accurate calculations of strongly correlated materials remain a formidable challenge in condensed matter physics, particularly due to the computational demand of conventional methods. This paper presents an efficient solver for dynamical mean field theory using configuration interaction (CI). The method is shown to have improved efficiency compared to traditional, exact diagonalization approaches. Hence, it provides an accessible, open-source alternative that can be executed on standard laptop computers or on supercomputers. The solver is demonstrated on cerium in the $\gamma$-, $\alpha$- and $\epsilon$-phases. An analysis of how the electronic structure of Ce evolves as function of lattice compression is made. It is argued that the electronic structure evolves from a localized nature of the 4f shell in $\gamma$-Ce to an essentially itinerant nature of the 4f shell of $\epsilon$-Ce. The transition between these two phases, as function of compression, can hence be seen as a Mott transition. However, this transition is intercepted by the strongly correlated $\alpha$-phase of elemental Ce, for which the 4f shell forms a Kondo singlet.