Avogadro

Avogadro is a free, open‑source tool for creating, editing, and visualizing molecular structures, crystals, biomolecules, and surfaces. It supports a wide range of geometry file formats for can write to many of them, and includes native parsers for output from quantum‑chemistry packages such as GAMESS, Gaussian, MOPAC, NWChem, and ORCA. The program’s multithreaded renderer and modern 3D graphics engine handle systems of thousands of atoms, while built‑in force fields quickly optimize hand‑drawn structures.

The interface is designed for both beginners and experienced researchers, offering intuitive sketching tools, animation capabilities, and various display options including reflections and ambient occlusion. Users can extend functionality through a plugin system; plugins may be written in Python or C++, and the community shares additional tools, force fields, and file‑format handlers.

Avogadro runs on Windows, Linux, and macOS, with support for Apple Silicon and future ARM Windows builds. It is released under a BSD 3‑clause license, with documentation, translations, and a responsive community available to assist users and contributors.