Testing and Application of Commercial Thermodynamics Software for Solid-Gas Equilibria in Planetary Science Applications

The ability to calculate chemical
equilibria from thermochemical constants (e.g., H, S,
Cp) or other experimental data is a tool widely
employed by scientists. However, phase equilibria for
planetary science problems is limited by easy access to
libraries of thermochemical data, as well as the software
to invert that data. Many academic software packages
are focused on specific types of problems (e.g., aqueous
solutions or melting and crystallization of magmas).
This focus makes them excellent tools for specific uses,
but poorer tools for other scenarios, especially those
involving elements or chemical species that are less
well-studied in that specific scientific field (e.g. NaCl
vapor).

Amongst the more general thermodynamic software
tools, there are closed academic software packages,
open-source options, as well as commercial software.
We have explored the extent to which commercial
chemistry/chemical engineering software may be able
to satisfy the need for thermochemical modeling
packages that can accommodate the diverse species and
conditions of planetary science problems. Here we
compare the output of software package HSC
Chemistry™ (Metso Outotec) to published vapor-solid
phase diagrams for a variety of major and minor
elements.

HSC Chemistry™ has been used in several recent
geochemical studies of terrestrial volcanic systems [2-
4]. However, it has not to our knowledge been
benchmarked against peer-reviewed model results for
the conditions and compositions relevant to planetary
science. We present one such comparison here, the low-
pressure environment of the solar nebula, using
literature data. In short, we find excellent agreement
between HSC Chemistry™ and the well-regarded
academic software package CONDOR. These
preliminary results suggest that at least some
commercial software packages are capable of robust
thermochemical calculations for planetary science.