Intellectual Merit. This is a proposal to develop open-source software tools for the creation and maintenance of ?internally consistent thermodynamic data/model collections? (ICTD/MCs). ICTD/MCs are intended to support assessment of phase relations in geochemical and petrologic systems and form the basis of several widely used thermodynamic modeling packages including MELTS, THERMO-CALC and Perple_X. The continued improvement of those thermochemical modeling packages depends principally on the ability to update and expand the underlying ICTD/MCs. Presently, that process is time-consuming and requires considerable expertise and technical ability in computer programming and numerical methods. The proposal objectives are (1) to make the process of calibrating these ICTD/MCs less cumbersome, (2) to incorporate, in a more intuitive way, modeling constraints that arise in application of ICTD/MCs to real world problems and to enable imposition of these constraints as inputs for calibration, and (3) to provide tools that will motivate a larger community of researchers to participate in the process of generating ICTD/MCs, thereby improving both quality and applicability, and raising the level of understanding of phase equilibrium modeling amongst geochemists and petrologists. The specific goals of this proposal are to produce open-source, open-platform software tools to (1) calculate and display phase equilibrium relations on pseudosections and on temperature-, pressure-, and thermodynamic state function-composition diagrams, subject to a variety of constraints (e.g., adiabatic, isochoric, isenthalpic) in both open and closed chemical systems, (2) assemble and maintain calibration data, such as that pertaining to experimental phase equilibrium reversal brackets, calorimetric data on thermodynamic properties (e.g., heat content, dynamic heat capacity, heat of solution) and physical property measurements that are applicable to calibration of equations of state or cation-ordering energetics in minerals, and (3) calibrate ICTD/MCs utilizing numerical/statistical methods consistent with linear programming, regression or Bayesian inference and provide tactile user feedback mechanisms that permit forward predictions to be adjusted in a self-consistent manner and thereby function as imposed constraints in the generation of alternate calibrations.

Broader Impacts. A significant amount of research and instruction in geochemistry and petrology relies upon thermodynamic modeling applications like geothermometry, geobarometry and phase diagram/phase equilibria calculators. These modeling tools are in turn based upon internally consistent thermodynamic data/model collections. Yet, the calibration of these ICTD/MCs remains a daunting exercise undertaken by just a few academic research groups and for-profit corporations, largely because of the intellectual and technical inertia associated with participation in the calibration activity. The result of this situation is that users of thermodynamic modeling tools are disconnected from efforts to expand and improve these tools; most users unfortunately treat these tools as mysterious ?black boxes.? The research proposed here aims to make the process of ICTD/MC calibration more accessible and intuitive, thereby empowering a broader community of users to improve the underlying thermodynamic framework. The proposed software infrastructure will motivate users to focus on the quality of data sources and the realism of predicted results rather than on the mechanics of the process of data bookkeeping, the implementation of calibration numerics, and the analysis of residuals. The proposed research will help users of thermodynamic modeling software better understand how those models are generated, how they can be improved, and what data or model enhancements are required to bring about that improvement.

National Science Foundation (NSF)
Division of Earth Sciences (EAR)
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Jennifer Wade
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Ofm Research
United States
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