Matter in Extreme Environments: Theoretical Studies of Light Elements Under Pressure

Despite their apparent simplicity, light elements at extreme conditions of pressure and temperature display remarkable properties that have fascinated theoreticians and experimentalists for over a century. Recent advances in first-principles simulation methods have allowed us to elucidate ever more properties of these materials giving us predictive capabilities which, when combined with continuously improving experimental platforms, allow us to obtain new insight into the behavior of matter at extreme conditions. In this talk I will present an overview of the current state of the art in first-principles simulation capabilities for light elements at extreme environments. I will pay particular attention to simulation methods that operate directly in the physical picture of electrons and ions, including density functional theory and quantum Monte Carlo. As a demonstrative example of the predictive capabilities of these methods, I will present recent predictions in the phase diagram of hydrogen during metallization and molecular dissociation in connection with recent experimental observations of metallization. I will present the most recent predictions for the location of the metal-insulator transition in the compressed liquid along with predictions of the optical properties near the dissociation regime. We show how state-of-the-art simulations are able to provide a comprehensive picture of molecular dissociation and metallization in the liquid which explains the conflicting experimental results obtained for several different platforms.