Unifying DFT+U approach for plutonium modeling

The theoretical description of the plutonium phase diagram still represents a major challenge to modern electronic structure methods. For the δ phase, a comprehensive knowledge has gradually been building up and the correct description of spectroscopic, magnetic, structural properties could be obtained using the DMFT approach. Effective Coulomb interactions in Pu were calculated very recently with DMFT and were found to be around 1 eV, which is much smaller than the "commonly accepted value" of 4 eV. It was also shown that the Hunds exchange, together with the spin-orbit coupling, yields an improved description of all phases, thus opening the way to a unifying theory of Pu.
In the present study, we investigate the influence of these weaker electron correlations on the ground state properties of the α, δ and ε phases of Pu, calculated with DFT+U (GGA), which is a static approximation of the DMFT.
We first show that the GGA+U+SOC and DMFT approaches yield similar structural properties. This allows us to use the "more simple" DFT+U approximation instead of the "expensive" DMFT to perform ab initio molecular dynamics calculations and extract temperature-dependent phonon spectra. GGA+U+SOC approximation allows for an improved description of all phases of Pu at high temperature.