is embedded in the C++ source, is in good agreement with Chianti.

Additionally we are starting to develop our own database, “Stout”. We will add new models of ions or molecules to this second database, and make it publicly available along with .

Molecular chemistry {#molchem}
-------------------

 initially included the chemistry network described by @Black1978 which was expanded to PDRs and XDRs as described by @Ferland1994. Nick Abel a massive upgrade to the heavy-element chemistry network as part of his PhD thesis, described in @Abel2004. Later refinements are discussed in @Abel2005, @Shaw2005, and @Shaw2006. Appendix A of @Abel2005 gives details of the numerical methods along with differences between UMIST and  reaction rates.  had predicted column densities for about 20 heavy element molecules, consisting of C and O atoms. It could not calculate physical conditions deep in a PDR or a molecular cloud, where most gas phase C, N, and O is in the form of molecules, due to numerical instabilities in the chemistry solver then used. The upgraded chemistry solver has no restrictions, as described in sections below.  now calculates the chemical abundance of 83 molecules using a network including $\sim 10^3$ chemical reactions involving molecules containing H, He, C, 