Electronic origin of the volume collapse in cerium

Abstract

The cerium $\ensuremath{\alpha}\ensuremath{-}\ensuremath{\gamma}$ 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 $T=0\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ 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 $p\ensuremath{-}f$ hybridization. The underlying mechanism unveiled by this work can hold in many Ce-bearing compounds, and more generally in other $f$-electron systems.