Papers › FastChem 2: An improved computer program to determine the gas-phase chemical...
FastChem 2: An improved computer program to determine the gas-phase chemical equilibrium composition for arbitrary element distributions
Joachim W. Stock, Daniel Kitzmann, A. Beate C. Patzer
The archive published only this paper's code-link row. Authors, date and abstract are from arXiv's metadata (CC0), read from the Kaggle arXiv metadata snapshot of 2026-09-12 where its title matched the archive's; the title is the archive's.
The computation of complex neutral/ionised chemical equilibrium compositions is invaluable to obtain scientific insights of, for example, the atmospheres of extrasolar planets and cool stars. We present FastChem 2, a new version of the established semi-analytical thermochemical equilibrium code FastChem. Whereas the original version is limited to atmospheres containing a significant amount of hydrogen, FastChem 2 is also applicable to chemical mixtures dominated by any other species, such as CO₂ or N₂. The new C++ code and an optional Python module are publicly available under the GPLv3 license at https://github.com/exoclime/FastChem. The program is backward compatible so that the previous version can be easily substituted. We updated the thermochemical database by adding HNC, FeH, TiH, Ca^-, and some organic molecules. In total 523 species are now in the thermochemical database including 28 chemical elements. The user can reduce the total number of species to, for example, increase the computation performance or can add further species if the thermochemical data are available. The program is validated against its previous version and extensively tested over an extended pressure-temperature grid with pressures ranging from 10⁻¹³ bar up to 10³ bar and temperatures between 100 K and 6000 K. FastChem 2 is successfully applied to a number of different scenarios including nitrogen, carbon, and oxygen-dominated atmospheres as well as test cases without hydrogen and helium. Averaged over the extended pressure-temperature grid FastChem 2 is up to 50 times faster than the previous version and is also applicable to situations not treatable with version 1.
Code
Repository list and official/mentioned flags are the archive's, frozen 2025-07-28. Reachability, where shown, is from one Syntology probe window (2026-09-16 to 2026-09-18); repositories not probed show nothing. GitHub stars are not tracked.
Code Syntology ran Syntology
Not run by Syntology. Nothing on this page verifies that the listed code works.
Results from the paper archive 2025-07-28
No leaderboard rows for this paper in the archive.
Report a problem or propose a change · a person checks every report against the paper or source before anything changes; decisions are listed on /corrections