Thermodynamic Properties and Phase Relations in Mantle Minerals Investigated by First Principles Quasiharmonic Theory

This research has been motivated by geophysics and materials physics. The objective of this research has been to advance materials theory and computations for high pressure and high temperature applications to the point that it can make a difference in our understanding of the Earth. Understanding of the mineralogy, composition, and thermal structure of the Earth evolves by close interaction of three fields: seismology, geodynamics, and mineral physics. Earth’s structure is imaged by seismology, which obtains body wave velocities and density throughout the Earth’s interior (Fig. 1). Interpretation of this data relies on knowledge of aggregate properties of Earth forming materials either measured in laboratory or calculated, in many cases by both. However, the conditions of the Earth’s interior, especially at the core, may be challenging for important experiments, and materials computations have emerged to contribute decisively to this field. Earth’s evolution is simulated by geodynamics, but these simulations need as input information about rheological and thermodynamic properties of minerals, including phase transformation properties such as Clapeyron slopes. Our research has concentrated on the phases of the Earth’s mantle, particularly the deep mantle whose conditions are more challenging for experiments. The mantle accounts for ~83% of the Earth’s volume. In this article we will review the essential first-principles approach used to investigate solids at high temperatures and pressures, summarize their performance for mantle minerals (Fig. 2), and point to critical results that have stirred us in the current research path. The success is remarkable, but some limitations point the way to future developments in this field.