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Methodology and Standards
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FreeGs referenceBibliographic reference
FreeGs: web-enabled thermodynamic database for modelling of geochemical processesEvgeniy N. Bastrakov1, Yuri V. Shvarov2, Stuart W. Girvan1, James S. Cleverley3, and Lesley A.I. Wyborn1 AbstractUsing multiple computer packages for modelling geochemical processes requires standardisation of the thermodynamic data underpinning such calculations. This is especially true for work 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 a comparison between performances of different packages on the basis of common data. The problem is further exacerbated by the tendency to collect and modify data on personal computers, resulting in multiple mutated data sets of variable quality and consistency. To overcome this problem, we have initiated the development of the FreeGs web-enabled database of thermodynamic properties hosted at Geoscience Australia. FreeGs aims to provide a single authoritative source available in real time to remote modelling applications via the Internet. This is one of the core activities of the Fluids and Modelling programs of the Predictive Mineral Discovery Cooperative Research Centre (pmd*CRC.) The initial FreeGs concept was suggested by the desktop UNITHERM database system that offers considerable flexibility in the choice of the data formats and integrated algorithms (Shvarov, 1999; Shvarov & Bastrakov, 1999). FreeGs contains mineral, gas, and aqueous species parameters that permit calculation of thermodynamic properties in a wide range of geological temperatures and pressures (0–1000°C, 1–5000 bar). It follows the main principle "multiple choices to multiple users". There is a choice of the depth of the database interrogation ("casual" or "novice" user vs an expert); the 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 already available via Web forms and reports. The next step is development of a web-feature service (WFS) that will enable users to calculate thermodynamic properties of species and chemical reactions at high T&P (eg, Δg(T,P) or log Kr(T,P)), and to output the recalculated data to clients computers and applications using XML. To ensure effective database maintenance, a group of experts will remotely contribute to FreeGs via the Web. This group compiles the data from literature and e-datasets, evaluates their quality and ensures their reasonable consistency, and makes them available via web forms and reports. This part of the project is run in collaboration with the Cooperative Research Centre for Landscape, Environment and Minerals (CRC LEME) to guarantee the seamless integration between low- and high-temperature geochemical modelling. AcknowledgmentsPublished with the permission of the CEOs, pmd*CRC, and Geoscience Australia. Related links |
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