Orbital entanglement in quantum chemistry

TL;DR

Orbital entanglement provides a powerful, intuitive framework for analyzing electron correlation, bond characteristics, and electronic wavefunction changes during chemical reactions, aiding interpretation and understanding of complex electronic structures.

Contribution

This paper reviews the application of orbital entanglement measures in quantum chemistry, highlighting their utility in analyzing electron correlation and chemical processes.

Findings

Orbital entanglement measures can dissect electron correlation effects.

It helps determine bond orders and assess active space calculations.

It monitors electronic wavefunction changes during reactions.

Abstract

The basic concepts of orbital entanglement and its application to chemistry are briefly reviewed. The calculation of orbital entanglement measures from correlated wavefunctions is discussed in terms of reduced $n$-particle density matrices. Possible simplifications in their evaluation are highlighted in case of seniority-zero wavefunctions. Specifically, orbital entanglement allows us to dissect electron correlation effects in its strong and weak contributions, to determine bond orders, to assess the quality and stability of active space calculations, to monitor chemical reactions, and to identify points along the reaction coordinate where electronic wavefunctions change drastically. Thus, orbital entanglement represents a useful and intuitive tool to interpret complex electronic wavefunctions and to facilitate a qualitative understanding of electronic structure and how it changes in chemical processes.