A Python-based electronic-structure package centered on coupled cluster, built on a
shared Wavefunction base that also hosts Hartree-Fock, MP2, and CI. Current capabilities
include:
- RHF-/UHF-/ROHF-based CCD, CC2, CCSD, CCSD(T), and CC3 energies
- Triples drivers for various approximate triples methods
- One- and two-electron (reduced) density matrices for CC2 and CCSD (with CC3 and (T) contributions)
- RHF-EOM-CCSD excitation energies
- Linear response functions (dynamic polarizability, optical rotation)
- Real-time (RT) CC2, CCSD, and CC3 with a selection of integrators
- Local (PAO, PNO, PNO++) CCSD energies, and local RT-CC
- Hartree-Fock (
HFwfn) MO-basis analytic derivative properties: energy gradient, static dipole polarizability, nuclear Hessian (force-constant matrix), atomic polar tensors (APTs / dipole derivatives), and atomic axial tensors (AATs) -- the building blocks for IR and VCD spectra - MP2 (
MPwfn) and CISD/CID (CIwfn) energies - GPU implementations for multiple methods
- Single- and mixed-precision arithmetic
Future plans:
- Quadratic response functions (in development)
- CC2 and CC3 excited states
- Analytic CC gradients
This repository is currently under development. To do a developmental install, download this repository and type pip install -e . in the repository directory.
This package requires the following:
Optional packages:
The docs/ directory holds the Sphinx documentation — a
getting-started guide with runnable examples and an
API reference. GitHub renders these .rst files in the browser; to
build the full HTML site locally, install Sphinx (and the Read the Docs theme) and run
make html from docs/.
T. Daniel Crawford, Benjamin G. Peyton, Zhe Wang, Jose Madriaga, Aparna Krishnan
Copyright (c) 2026, T. Daniel Crawford
Project structure based on the MolSSI's Computational Molecular Science Python Cookiecutter Version 1.5.