# Multireference Stochastic Coupled Cluster

## TL;DR

This paper introduces a stochastic multireference coupled cluster method that effectively handles strong electron correlation by incorporating multiple reference determinants, enhancing the flexibility and insight of electronic structure calculations.

## Contribution

It presents a novel modification of stochastic coupled cluster that includes multiple references, improving the description of strongly correlated systems.

## Key findings

- Successfully describes strongly correlated molecules with few references
- Maintains the advantages of single reference stochastic coupled cluster
- Provides flexible control over references and excitations

## Abstract

We describe a modification of the stochastic coupled cluster algorithm that allows the use of multiple reference determinants. By considering the secondary references as excitations of the primary reference and using them to change the acceptance criteria for selection and spawning, we obtain a simple form of stochastic multireference coupled cluster which preserves the appealing aspects of the single reference approach. The method is able to successfully describe strongly correlated molecular systems using few references and low cluster truncation levels, showing promise as a tool to tackle strong correlation in more general systems. Moreover, it allows simple and comprehensive control of the included references and excitors thereof, and this flexibility can be taken advantage of to gain insight into some of the inner workings of established electronic structure methods.