1)  Grain and gas temperature and relation (10 K, fixed)
2)  Ad hoc formation of H$_{2}$ on grain surfaces (off) - Ad hoc formation of H$_{2}$ dedicates half of the adsorbed H (Both surface and bulk) for only H$_{2}$ formation reactions. The other half of H is available for all other reactions, minus the H$_{2}$ formation reactions.
3)  H$_{2}$ self-shielding (on) - \citep{lee_photodissociation_1996}
4)  CO self-shielding (on) - \citep{visser_photodissociation_2009}
5)  N$_{2}$ self-shielding (on) - \citep{li_photodissociation_2013}
6)  Photodesorption of ices (on) - allows for photon-induced desorption of molecules from ice grain surfaces.
7)  Cosmic ray induced diffusion (off) - diffusion based on heating from cosmic ray collisions with grains. Off due to whole grain cosmic ray heating allowing for faster diffusion as well as thermal desorption. 
8)  Eley-Rideal and complex-induced rx mechanisms  (off) - \citep{ruaud_modelling_2015}
9)  Competitive H$_{2}$ grain tunneling mechanism (fastest) - \citep{herbst_complex_2009}
10) Modified rates (off) - modifies diffusion rates to be the maximum of evaporation or accretion rates.
11) Species Conservation (electrons only) - checks to make sure we are not creating or destroying electrons or elements.