Many-body electronic structure from quantum Monte Carlo for f-electron materials

The electronic structure of actinides is complicated by the presence of f-electrons, where strong correlation and spin-orbit coupling drive a subtle competition between itinerant and localized behavior that is poorly resolved by conventional mean-field methods such as density functional theory.  Explicitly correlated methods such as quantum Monte Carlo (QMC) are ideally suited to capture these effects, yet their application to f-electron materials has so far been limited. In this talk, we highlight some methodological developments aimed at bringing QMC to bear on bulk uranium and various uranium compounds. First, we discuss the development of a correlation consistent effective core potential for uranium which significantly improves the accuracy of the underlying Hamiltonian. Second, we derive and implement a novel stress estimator within QMC enabling direct enthalpy minimization and geometry optimization under pressure. Together, these developments open the door to computing accurate cold curves, including phase transitions, of uranium materials from QMC for the first time.