FreeGs: A web-enabled thermodynamic database for geochemical modelling

Using multiple computer packages for modelling geochemical processes requires standardisation of the thermodynamic data. This is critical in a “virtual” collaborative environment, where remote researchers, with different skill sets and levels of thermodynamic literacy, work on the same or similar problems. Standardisation is hindered by multiple sources of recommended thermodynamic data, disparities in speciation models, different models for extrapolation of thermodynamic properties, and program-specific database formats. This situation often precludes the choice of the best (or the favourite) package for the problem at hand, or benchmarking different packages on the basis of common data. The problem is exacerbated by the tendency to collect and modify data on personal computers, resulting in multiple mutated data sets of variable quality and consistency. The Predictive Mineral Discovery Cooperative Research Centre (pmd*CRC), has established FreeGs: a web-enabled database of thermodynamic properties hosted at Geoscience Australia. FreeGs contains mineral, gas, and aqueous species parameters that permit calculation of thermodynamic properties within a wide range of geological temperatures and pressures. The database provides a choice of the depth of the database interrogation (“casual” or “novice” user vs an expert); a choice of the data versions (“recommended” values for the species of interest vs all the available data); a choice of the available extrapolation models (equations of state); and a choice of formats of the output data. Storage and access to primary FreeGs data are available via Web forms and reports. An integrated software enables users to calculate thermodynamic properties of species and chemical reactions at high T&P (e.g., ∆g(T,P) or logKr(T,P)). In future, users’ applications will be able to acces the system as a web-service using XML. The project is run in collaboration with the Cooperative Research Centre for Landscape Environments and Mineral Exploration (CRCLEME). The URL is www.ga.gov.au/rural/projects/geofluids.jsp A modified hydrogen electrode concentration cell (HECC): Study of scheelite solubility