Valence1

Valence1 is a software library designed to support researchers in computational chemistry, particularly those working with electronic structure and valence state analysis. The project was initially released in 2019 by a team of developers at the Institute for Theoretical Chemistry. It provides a set of Python modules that can be integrated into existing workflows for quantum chemical calculations. The library offers tools for calculating valence electron distributions, generating valence diagrams, and performing automated checks for valence consistency in molecular models.

Key features of Valence1 include a lightweight API that accepts output files from popular quantum chemistry packages such as Gaussian, ORCA, and Q-Chem. It can parse Hartree–Fock, DFT, and post-Hartree–Fock results to extract atomic charges and electron populations. The library also supplies visualization utilities to create valence diagrams directly from calculated data, enabling quick identification of anomalies such as over‑ or under‑filled shells. Users can extend Valence1 by defining custom valence rules for non‑standard elements or organometallic complexes.

The project is distributed under the MIT License and is maintained on GitHub, where issue tracking and pull requests are actively managed. Documentation is available in the repository’s wiki, offering tutorials and example scripts. As of 2024, Valence1 has been cited in over 30 peer‑reviewed papers, including studies on transition‑metal catalysis and aromaticity. Its open‑source nature encourages contributions from the broader computational chemistry community.