The Master Chemical Mechanism
The Browse facility enables the user to look through the MCM by VOC species category. All species have associated chemical structures, allowing recognition of the more complex species, that cannot be identified through their necessarily succinct MCM species names. All the primary VOCs are listed by category along with an inorganic chemistry section. Listings are also provided for the generic rate coefficients used throughout the MCM, including the photolysis rate parameterisations for the organic compounds
The Search function allows the user to search the MCM for specific compounds and their degradation mechanisms, either with the appropriate SMILES string (a link to a SMILES tutorial is provided), InChI or the MCM species name. A facility for entering a drawing of the sought species structure is also available, or for searching for species with a specific molecular weight or within a range of molecular weights. The search results will return the structure(s) of the species and the designated MCM name(s).
If the MCM species name is then clicked, the user is led to its degradation scheme. Each individual reaction within the reaction listing displays its rate coefficient and branching ratio as well as reactant and product structural information. Any generic rate coefficients and photolysis rates are directly linked to the appropriate table which lists the equations and parameters used to calculate their value. Each reaction product’s degradation scheme can be accessed in a similar fashion by clicking on its MCM species name. Also individual reactants and products have an associated “mark” button so that they can be added to (and displayed in) the Mark List for complete mechanism extraction later.
Linked to each reaction equation is a “doc” link. This leads to a webpage containing contextual information from the MCM protocols on where the rate coefficients and branching ratios come from or how they were calculated (e.g. from a suitable structure activity relationship). The protocol web pages are linked to a central citations database which contains a list of references complete with abstract (where available).”
The Extract web-tool can extract complete subset mechanisms of the MCM for the species listed in the Mark List. The MCM can be extracted in various formats including FACSIMILE, KPP , FORTRAN, and XML , therefore making the MCM more accessible to an increasingly wide range of modellers. New extraction output formats will continue to be developed through the interaction with the user community.