# New Strategies in Modeling Electronic Structures and Properties with Applications to Actinides

## TL;DR

This chapter reviews advanced quantum chemical methods for modeling electronic structures of heavy-element compounds, emphasizing relativistic effects, multi-reference approaches, and insights from quantum information theory.

## Contribution

It provides a comprehensive overview of modern electronic structure methods tailored for actinides, integrating relativistic Hamiltonians and quantum information concepts.

## Key findings

- Comparison of relativistic Hamiltonians for heavy elements
- Analysis of multi-reference quantum chemistry methods
- Application of quantum information theory to complex electronic structures

## Abstract

This chapter discusses contemporary quantum chemical methods and provides general insights into modern electronic structure theory with a focus on heavy-element-containing compounds. We first give a short overview of relativistic Hamiltonians that are frequently applied to account for relativistic effects. Then, we scrutinize various quantum chemistry methods that approximate the $N$-electron wave function. In this respect, we will review the most popular single- and multi-reference approaches that have been developed to model the multi-reference nature of heavy element compounds and their ground- and excited-state electronic structures. Specifically, we introduce various flavors of post-Hartree--Fock methods and optimization schemes like the complete active space self-consistent field method, the configuration interaction approach, the Fock-space coupled cluster model, the pair-coupled cluster doubles ansatz, also known as the antisymmetric product of 1 reference orbital geminal, and the density matrix renormalization group algorithm. Furthermore, we will illustrate how concepts of quantum information theory provide us with a qualitative understanding of complex electronic structures using the picture of interacting orbitals. While modern quantum chemistry facilitates a quantitative description of atoms and molecules as well as their properties, concepts of quantum information theory offer new strategies for a qualitative interpretation that can shed new light onto the chemistry of complex molecular compounds.