The experimental construction of phase diagrams requires accurate and well-equilibrated thermo-physical measurements to obtain thermodynamic equilibrium. Hence, it took many decades to map the phase space of thousands of binary systems at ambient conditions. Pressure affects phase diagrams both by altering the interactions, which control the nature of the diagram and through the emergence of new phases and phase boundaries. However, measuring thermophysical properties under pressure is challenging due to technical difficulties in pressure cells, pressure, and temperature gradients, which make it hard to locate phase transitions. Therefore, it is useful to combine experimental measurements and thermodynamic modeling to explore the pressure evolution of alloy systems.

We report on the pressure evolution of several alloy systems studied through a combination of experimental techniques and thermodynamic modeling. Specifically, the isomorphous Bi-Sb, eutectic Ga-In, monotectic Bi-Ga with a liquid miscibility gap, and the ternary Bi-Sb-Pb systems. Through a thermodynamic model, supported by physical measurements of sound velocity and density, we were able to construct phase diagrams up to several GPa of these alloys. To validate our predictions, we undertook high-pressure measurements, including x-ray diffraction in a diamond anvil cell (DAC), resistivity, and differential thermal analysis (DTA) in a Paris-Edinburgh (PE) large volume press. These studies validate our thermodynamic model predictions of the pressure dependence of the alloy systems; including changes in the nature of the diagram from isomorphous to eutectic, disappearance of the miscibility gap, shifts of eutectic points and the evolution of interaction parameters with pressure. 

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