MULTI-STEP: Multiscale Stress-drivenThermodynamic Equilibrium Predictions

• Applicant: Professorin Dr. Lucie Tajcmanova
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 568808937

Under specific environmental conditions, such as varying pressure and temperature, rocks and metals undergo phase transformations to achieve thermodynamic equilibrium. These transformations can significantly influence the mechanical properties of natural and engineered materials.Studying mineral assemblages offers critical insights into their formation conditions, enabling the reconstruction of key geodynamic processes, including orogenesis, rifting, or subduction. In metallic materials, the development of multiple phases is critical for optimizing performance.In both the Earth Science and Metallurgy communities, the computation of phase stability fields relies on two fundamental hypotheses:i) Pressure controlling transformation is a static and scalar measure of stress;ii) Deviatoric stresses do not impact phase equilibrium.Such hypotheses, however, have recently triggered discussions in both communities.In this context, our project proposes to overcome the classical hypotheses for phase equilibrium calculations using a multiscale numerical approach, from atomistic to large-scale thermomechanical modeling, coupled with micromechanical experiments. Atomistic simulations are optimal tools to compute free energies and infer phase diagrams under varying thermomechanical conditions (e.g., deviatoric stress).By cross-validating with both existing and newly acquired experimental data, the computed non-hydrostatic phase diagrams will be used in continuum modeling frameworks from microstructural to geodynamical scales.The methodology will first be developed for the α/ω transformation of titanium, which is a major microstructural evolution mechanism for which extensive experimental data exist. Then, the proposed approach will be applied to the polymorphic quartz–coesite transition, a key boundary in ultrahigh-pressure metamorphism (pressure above 2.7 GPa), which is crucial for understanding major geodynamic processes.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partners: Dr. Jean Furstoss; Professor Dr.-Ing. Daniel Pino Muñoz