Alloy thermodynamics

Alloy thermodynamics at high pressures from first principles calculations

Phase diagrams of the elements in pressure-temperature phase space and of alloys in the pressure-temperature-composition phase space are of fundamental importance for modeling materials behavior in a wide range of environments, ranging from technological to geophysical systems. Furthermore, the study of the phases of matter continues to produce new and exciting physical phenomena, e.g. new high pressure structures and liquid-liquid phase transitions.

Traditionally phase diagrams were constructed empirically. However, for many systems of interest, the necessary experimental information is either not, or only partially, available due to the extreme conditions required or the nature of the materials in the system. Furthermore, for some applications it is desirable to have knowledge of the phase diagram and the physical properties beyond the region of stability which is accessible empirically.

Constructing phase diagrams theoretically is conceptually simple. All that is required is a good Hamiltonian describing the system. In practice, the construction of phase diagrams is a challenge, requiring methods to select the underlying crystal structures as well as to determine the free energy of the different phases. In this project we model the phase diagrams of multi-phase elements which exhibit high temperature phase transitions. Using this information we shall address the modeling of binary alloys of these elements which are reported to form solid solutions.