A newly-developed hybrid computational method has computed, for the first time, plutonium’s exotic crystal structure transformations and additionally calculated the volume-collapse transition of praseodymium. As plutonium is heated it undergoes six complex crystalline phase transitions—the most of any element at ambient pressure. Explaining these six different phases has been a long-standing challenge of solid-state physics. These calculations are the first theoretical description of all of the crystal phases of plutonium that agree with the experimental data. In addition to plutonium, the team calculated the phase changes of praseodymium. The study shows that its volume-collapse transition, contrary to its periodic table neighbor, cerium, would not occur without a change in the lattice structure. Plutonium and praseodymium are prototypical examples of strongly correlated materials—a wide class of materials that display unusual properties due to how the electrons interact. The new computational method accounts for these interactions, leading to a better explanation of element properties. The new algorithm is a cost-effective and user-friendly method that will enable researchers to calculate the metamorphoses of a variety of strongly correlated materials.
Phase Diagram and Electronic Structure of Praseodymium and Plutonium