Pythonic Black-box Electronic Structure Tool (PyBEST). An open-source Python platform for electronic structure calculations at the interface between chemistry and physics

TL;DR

PyBEST is an open-source Python-based electronic structure software that integrates advanced methods, analysis, and visualization tools, facilitating large-scale calculations and interface with other packages for chemistry and physics research.

Contribution

The paper introduces PyBEST, a modular, Python-centric electronic structure platform with unique methods and analysis tools, optimized for large-scale calculations and easy integration.

Findings

Successfully performed orbital optimization on a 190-electron, 777-orbital vitamin B12 model

Demonstrated PyBEST's capability for large-scale electronic structure calculations

Validated methods with tests on a 1-D model Hamiltonian

Abstract

Pythonic Black-box Electronic Structure Tool (PyBEST) represents a fully-fledged modern electronic structure software package developed at Nicolaus Copernicus University in Toru\'n. The package provides an efficient and reliable platform for electronic structure calculations at the interface between chemistry and physics using unique electronic structure methods, analysis tools, and visualization. Examples are the (orbital-optimized) pCCD-based models for ground- and excited-states electronic structure calculations as well as the quantum entanglement analysis framework based on the single-orbital entropy and orbital-pair mutual information. PyBEST is written primarily in the Python3 programming language with additional parts written in C++, which are interfaced using Pybind11, a lightweight header-only library. By construction, PyBEST is easy to use, to code, and to interface with other software packages. Moreover, its modularity allows us to conveniently host additional Python packages and software libraries in future releases to enhance its performance. The electronic structure methods available in PyBEST are tested for the half-filled 1-D model Hamiltonian. The capability of PyBEST to perform large-scale electronic structure calculations is demonstrated for the model vitamin B12 compound. The investigated molecule is composed of 190 electrons and 777 orbitals for which an orbital optimization within pCCD and an orbital entanglement and correlation analysis are performed for the first time.