# The Penguin program

The Penguin program is an open-source Python program that enables molecular property and spectroscopy calculations using coupled cluster theory and perturbation theory approaches such as cluster perturbation theory and Møller-Plesset perturbation theory.

The program is under continous development and so is this documentation.  
This was compiled on {{ today }}.  

## Functionalities

Coupled Cluster Theory

Cluster Perturbation Theory

Møller-Plesset Perturbation Theory

## Source Code(s)

[The GitLab source repository](https://gitlab.com/Penguinprogram/penguin)

[The GitLab manual repository](https://gitlab.com/Penguinprogram/penguinman)

[The GitLab matrix element repository](https://gitlab.com/Penguinprogram/mel)

## Citation

When citing the Penguin program, use the following citation:  
  
```
@article{doi:10.1021/acs.jpca.5c02513,
author = {Hillers-Bendtsen, Andreas Erbs and Johansen, Magnus Bukhave and von Buchwald, Theo Juncker and D{\"u}nweber, Phillip Gustav Iuel Luno̷e and Olsen, Lars Henrik and Rask, Laust and Junker, Georg Ingvartsen and Knudsen, Rasmine Maria Hansen and Mikkelsen, Kurt V.},
title = {Penguin: A Python-Based Program for Electronic Structure Calculations Based on Coupled Cluster Theory},
journal = {The Journal of Physical Chemistry A},
volume = {129},
number = {45},
pages = {10571-10582},
year = {2025},
doi = {10.1021/acs.jpca.5c02513},
    note ={PMID: 41144650},
URL = {https://doi.org/10.1021/acs.jpca.5c02513}
}
```