# Generalized self-energy embedding theory

## TL;DR

This paper introduces a generalized form of self-energy embedding theory (SEET) that enables efficient quantum chemistry calculations for large active spaces by dividing orbitals into intersecting groups for parallel processing.

## Contribution

It extends SEET to handle larger active spaces through intersecting orbital groups, allowing scalable and parallelizable quantum chemistry computations.

## Key findings

- Generalized SEET performs comparably to full active space treatments.
- Parallel calculations on orbital groups improve computational efficiency.
- The method offers a hierarchy of systematically improvable approximations.

## Abstract

Ab initio quantum chemistry calculations for systems with large active spaces are notoriously difficult and cannot be successfully tackled by standard methods. In this letter, we generalize a Green's function QM/QM embedding method called self-energy embedding theory (SEET) that has the potential to be successfully employed to treat large active spaces. In generalized SEET, active orbitals are grouped into intersecting groups of few orbitals allowing us to perform multiple parallel calculations yielding results comparable to the full active space treatment. We examine generalized SEET on a series of examples and discuss a hierarchy of systematically improvable approximations.