Structure Search on H₂-PRE Phase of Solid Hydrogen: Diffusion Monte Carlo Study

The structural phase diagram of solid hydrogen is important for condensed matter physics and planetary science. However, the different structures in the phase diagram are still debated due to the experimental difficulties at extreme conditions. Therefore, an accurate ab initio structure search is crucial to assist experiment. We used a combination of structural search algorithms, density functional theory and diffusion Monte Carlo methods to study the problem. We eventually found a new stable structure, P2₁/c-8, stable under high pressures of 400 – 600 GPa. Our predicted pressure range for P2₁/c-8's appearance correlates well with a phase found experimentally in hydrogen by infrared spectroscopy. In this talk, we will describe the context of our work from the simulation point of view. We will discuss our results in connection with the experimental evidence and other theoretical predictions.