Global Chemical Equilibrium Code Documentation

A high-performance numerical framework designed to simulate the multi-phase chemical interactions between a planet’s atmosphere, magma ocean, and metallic core.

Main Authors: Simon Grimm, Aaron Werlen, Annika Salmi, Caroline Dorn. ETH Zürich, Switzerland.

Based on the Chemical Equilibrium Code from Hilke Schlichting and Edward Young (2022).

• License
• Requirements
• Code Versions
• The Chemical Network (Standard Version)
  • Reaction equations for condition for equilibrium
  • Mass balance equations
  • Mole fraction sums
  • The Pressure equation
  • The Cost Function
• The Carbon Version
• The Sulfur Nitrogen Version
• The Young 2023 Version
• Tutorial
  • Step 1: Modify the chemical network equations file Equations.py
  • Step 2: Test the Equations.py file
  • Step 3: Generating and compiling the C++ code
  • Step 4: Provide the Gibbs free energies
  • Step 5: Run the code
• Files
  • The initial conditions file, initial.dat
  • The chem_input.dat file
  • The code parameters file param.dat
  • The output file
  • The info.dat file
• Solvers
  • General solver strategy
  • Optimizers
• Gibbs energies
  • 1) Use the Gibbs.py python code to generate the Gibbs energies on the fly
  • 2) Use the Gibbs.py python code to generate the Gibbs energy file
  • 3) Use a Gibbs energy file

[WDS+25]

Aaron Werlen, Caroline Dorn, Hilke E. Schlichting, Simon L. Grimm, and Edward D. Young. Atmospheric c/o ratios of sub-neptunes with magma oceans: homemade rather than inherited. The Astrophysical Journal Letters, 988(2):L55, jul 2025. URL: https://doi.org/10.3847/2041-8213/adf185, doi:10.3847/2041-8213/adf185.

[SchlichtingYoung22]

Hilke E. Schlichting and Edward D. Young. Chemical Equilibrium between Cores, Mantles, and Atmospheres of Super-Earths and Sub-Neptunes and Implications for Their Compositions, Interiors, and Evolution. \psj , 3(5):127, May 2022. arXiv:2107.10405, doi:10.3847/PSJ/ac68e6.

[YoungShaharSchlichting23]

Edward D. Young, Anat Shahar, and Hilke E. Schlichting. Earth shaped by primordial H$_2$ atmospheres. \nat , 616(7956):306–311, April 2023. arXiv:2304.07845, doi:10.1038/s41586-023-05823-0.