Electronic origin of the volume collapse in cerium

The cerium alpha-gamma phase transition is characterized by means of a many-body Jastrow-correlated wave function, which minimizes the variational energy of the first-principles scalar-relativistic Hamiltonian, and includes correlation effects in a nonperturbative way. Our variational ansatz accurately reproduces the structural properties of the two phases, and proves that even at temperature T = 0 K the system undergoes a first-order transition, with ab initio parameters which are seamlessly connected to the ones measured by experiment at finite T. We show that the transition is related to a complex rearrangement of the electronic structure, with a key role played by the p-f hybridization. The underlying mechanism unveiled by this work can hold in many Ce-bearing compounds, and more generally in other f -electron systems.