GEOSH: Chemical Equilibrium Calculations of Ideal Gas Mixtures

Understanding the relative abundances of atoms, molecules, and ions in a gaseous mixture at equilibrium is necessary when modeling gaseous mixtures in a wide range of applications such as planetary and stellar atmospheres. To simplify the problem, we apply the law of mass action and Saha-Langmuir equations to express the chemical species in terms of the atomic species present in the system. By normalizing chemical species and eliminating electron capture and ionization degrees of freedom, we reduce the problem to a set of non-linear equations describing the conservation of each atomic nuclei and charge species. We introduce GEOSH, a code designed to solve for the relative concentrations of chemical species by solving a system of non-linear equations using a Newton-Raphson solver while determining the thermodynamic quantities of the system in equilibrium.