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Welcome to the documentation for the easyxtb Python package.
Introduction
easyxtb is an unofficial API for the xtb and CREST semi-empirical quantum chemistry programs with an emphasis on intuitive and straightforward usage.
It forms the basis for avo_xtb, a plugin for the 3D chemical visualization software Avogadro 2 that provides an in-app interface to the xtb program for quick and accurate calculations, as well as the CREST program for extended functionality.
The Python package easyxtb can be used independently of avo_xtb as an interface to launch calculations and process their results from Python.
xtb is developed by the Grimme group in Bonn and carries out semi-empirical quantum mechanical calculations using the group's extended Tight-Binding methods, referred to as "GFNn-xTB".
These methods provide fast and reasonably accurate calculation of Geometries, Frequencies, and Non-covalent interactions for molecular systems with up to roughly 1000 atoms, with broad coverage of the periodic table up to Z = 86 (radon).
crest (Conformer–Rotamer Ensemble Sampling Tool) adds a variety of sampling procedures for several interesting applications including conformer searches, thermochemistry, and solvation.
Usage
For an overview on how to use the package, see Getting started.
The remaining pages in the documentation cover the user-facing parts of the Python API in more detail.
Further reading
For more detail on the meaning of each program's runtypes and command line options, see their documentation: