Welcome to PyCI Documentation!

Welcome to PyCI Documentation!#

PyCI is a free, open-source, and cross-platform Python library designed to help you effortlessly run arbitrary determinant CI. Please use the following citation in any publication using PyCI library:

“PyCI: A Python-scriptable library for arbitrary determinant CI”: Michelle Richer, Gabriela Sánchez-Díaz, Farnaz Heidar-Zadeh, Marco Martínez González, Valerii Chuiko, and Paul W. Ayers

The PyCI source code is hosted on GitHub and is released under the GNU General Public License version 3 (GPLv3). We welcome any contributions to the PyCI library in accordance with our Code of Conduct; please see our Contributing Guidelines. Please report any issues you encounter while using GBasis library on GitHub Issues. For further information and inquiries please contact us at qcdevs@gmail.com.

Why PyCI?#

PyCI is a versatile, free, and open-source Python 3 library designed for setting up and executing arbitrary determinant CI (Configuration Interaction) and FanCI (Flexible Ansatz for N-electron Configuration Interaction) computations. This library is your gateway to efficiently generate arbitrary sets of Slater determinants and construct selected CI wave functions through intuitive Python scripting.

Key Features:#

  1. Flexible CI Computations: Seamlessly set up and run arbitrary determinant CI and FanCI computations with ease.

  2. Python Scripting: Construct CI wave functions through Python scripting, allowing for unprecedented flexibility and control.

  3. FanCI Wave Functions: Build arbitrary FanCI wave functions by implementing overlap functions and gradients into a well-defined Python interface.

  4. Efficient Multi-threading: PyCI leverages a core C++ library with multi-threading capabilities for optimized (Fan)CI computations.

  5. ENPT2 Energy Correction: Compute second-order Epstein-Nesbet perturbation theory (ENPT2) energy corrections effortlessly.

  6. RDM Calculations: Calculate spin-polarized one- and two-electron (transition) Reduced Density Matrices (RDMs) of wave functions.

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